risk factors of low back pain among filipino male air-conditioned bus drivers
DESCRIPTION
A research paper on the risk factors of low back pain affection drivers of air-conditioned buses in the Philippines.TRANSCRIPT
Risk Factors of Low Back Pain Among Filipino Male
Air-conditioned Bus Drivers
A Research Presented to The Special Studies Committee
of the College of Public Health
University of the Philippines, Manila
In Partial Fulfillment of the Requirements In PH 199
Submitted by Group 8 Gail M. Culla
Felicidad Clare S. Martinez Jay Patrick R. Santiago
Mia Marie M. Tad-y
Adviser Benjamin C. Vitasa, MD, MPH, PhD
23 February 2004
Abstract
The general objective of the study is to determine the risk factors associated with low back pain among Filipino male air-conditioned bus drivers. It specifically aims to describe the distribution of bus drivers according to age, long driving time, vibration exposure, long distance driving, duration of employment, driving posture, seat/workplace design and psychological factors; describe the distribution of bus drivers with low back pain by age, long driving time, vibration exposure, long distance driving, driving posture, seat/workplace design, and psychological factors; and determine the association of different risk factors with low back pain adjusting for the effects of confounders and other independent variables. An analytical cross-sectional design was used. Three hundred seventy-eight drivers of air-conditioned buses from eight bus companies located in an urban cluster of bus stations were included as subjects. A self-administered questionnaire was given to each subject to obtain data on independent variables such as demography, long distance driving, driving posture, seat design, vibration exposure, duration of employment as a bus driver, psychological factors and long driving time. Anthropometric data were gathered using a tape measure. The outcome variable, low back pain was assessed based on questions asked in the questionnaire, using as inclusion criteria, chronicity of at least 6 months, recurring at least twice a week and 30 minutes duration per experience of pain. Using logistic regression, the association of risk factors with low back pain was determined. The identified risk factors included age, insufficient work space, abnormal vibration, uncomfortable sitting posture, constrained posture, rough roads, boredom, depression, frequent movement of back, frequent movement of shoulders, long distance driving, long driving time, vibration exposure, employee satisfaction with management and height.
Results showed that constrained posture, long distance driving and employee satisfaction with management were significantly associated with low back pain. Drivers with any one of these characteristics have greater odds of having low back pain of 3, 2.2 and 2, respectively.
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1.0 Introduction
Transportation through a vehicle allows movement from an origin to its
destination. Through driving, the course of a vehicle is controlled. For commuters,
traveling by land would not be possible without the vehicle and the driver himself.
Drivers are people who consider driving as their profession and source of income. It
is of great importance for them to know that aside from the benefits they can get
from this job, their life can still be at risk. Aside from possible accidents due to work,
their health can also be at risk. Low back pain is a form of occupation-related
disease which may cause increased cases of absenteeism and lesser productivity
for the working population. Drivers, as part of this population, should be aware that
this health issue is not a minor problem and should be taken seriously because it
can affect them directly and even their employers.
All over the world, several studies on low back pain have been conducted but
only few have established its association with driving a bus. No known Philippine
study on low back pain among bus drivers exists. Bus driving is only one of many
jobs that persons with a driver’s license can go into. Having little knowledge on the
possible occurrence of low back pain due to driving and its prevention can adversely
affect the health and productivity of bus drivers. For these reasons, a study to
establish the association between long driving time and low back pain is important
and timely. Recommendations on the prevention of low back pain can be formulated
based on the study.
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2.0 Review of Related Literature
Low back pain (LBP) is chronic pain localized in the lumbo-sacral spine with
acute and sudden onset lasting for about thirty minutes and is intermittent and
recurring for at least twice a week for six months. It is the most common cause of
occupational disability in the industrialized societies and together with headache, is
the most frequent variety of pain which workers have to contend with. However,
physicians diagnose low back pain as acute if it lasts less than a month and is not
caused by serious medical conditions. Most cases clear up in a few days without
medical attention although recurrence after a first attack is common (1).
2.1. Epidemiology of Low Back Pain
Between 60% and 90% of the general population experience back pain at one
time or another during their lifetimes. In a study done in Denmark, it was noted that
40% of the general population had recurrent LBP in 5 years (2). A cross-sectional
study done in Nigeria among office workers revealed that 38% suffer from episodes
of LBP in a 12-month period (3). Another cross-sectional study showed that 60% of
women in a textile factory in Vietnam suffer the same condition (4). Greater in
magnitude is the 73%-76% prevalence of LBP among nurses in Switzerland shown
in an eight-year cohort study (5). Every year, nearly 15% of American adults visit
their doctors because of low back pain episodes (6). These data were gathered
through questionnaires, observations, interviews and health records.
Men and women are equally at risk. Low back pain is second to upper
respiratory infection as the reason for seeing a doctor. In the US, its cost is second
to cancer and heart disease. The Center for Disease Control reported that in 1995,
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over 20 million visits to physicians and clinics were related to back symptoms. Low
back pain occurred in 25% of the working population and the economic impact in the
United States has been estimated to be over $75 billion per year (6). According to
the National Research Council and the Institute of Medicine of the National
Academies, it affects about 1 million workers and costs the nation between $45
billion and $54 billion in compensation expenditures, lost wages and decreased
productivity annually (7).
The majority of patients with low back pain state that they have increased
pain while sitting or upon arising from sitting. It is believed that almost all LBP is
aggravated and perpetuated by poor sitting posture in both sedentary and manual
workers.
2.2. Low Back Pain and Driving
Several studies have shown the statistically significant relationship between
LBP and driving. In a cross-sectional study done in Denmark, the prevalence of
frequent low back pain among urban bus drivers was 57% (2). This figure is not far
from the 56.62% LBP prevalence seen among bus drivers in Lithuania (8).
However, the figure is slightly lower in a study done among Japanese truck drivers.
From 153 respondents, the prevalence of LBP in one month was 50.3% (9).
2.3. Anatomy and Pathophysiology of Low Back Pain
The important functions that the lower back or lumbar area serves for the
human body include structural support, movement and protection of certain body
tissues. It holds most of the body’s weight and is involved in bending, extending or
rotating at the waist. The lumbar spine and muscles protect the soft tissues of the
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nervous system and spinal cord as well as adjacent organs of the pelvis and
abdomen (10).
The lumbar spine is composed of vertebrae “stacked” together that forms a
movable support structure and protects the spinal cord from injury. Each vertebra
possesses a spinous process, a bony prominence behind the spinal cord, which
shields the cord's nervous tissue. There is also a strong bony "body" in front of the
spinal cord to provide a platform suitable for weight-bearing. The lumbar vertebrae
stack immediately atop the sacrum bone in between the buttocks. On each side, the
sacrum meets the iliac bone of the pelvis to form the sacroiliac joint of the buttocks
(10).
The discs are pads that serve as "cushions" between each vertebral body
which minimize the impact on the spinal column. Each disc is designed like a jelly
doughnut with a central softer component, the nucleus pulposus, which is capable of
rupturing or herniating through the surrounding outer ring, the annulus fibrosus, and,
thereby, irritating adjacent nervous tissue (10).
Ligaments are strong fibrous soft tissues that firmly attach bone to bone.
Ligaments attach each of the vertebrae and surround each of the discs (10).
The nerves that provide sensation and stimulate the muscles of the low back
as well as the lower extremities (the thighs, legs, feet, and toes) exit the spinal
column through bony portals called "foramen" (10).
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Many muscle groups which are responsible for flexing, extending, and
rotating the waist, as well as moving the lower extremities attach to the lumbar spine
through tendon insertions (10).
The aorta and blood vessels that transport blood to and from the lower
extremities pass in front of the lumbar spine into the abdomen and pelvis.
Surrounding these blood vessels are lymph glands and involuntary nervous system
tissues which are important in maintaining bladder and bowel control (10).
The uterus and ovaries are important pelvic structures in front of the lumbar
area of women. The prostate gland is a significant pelvic structure in men. The
kidneys are on either side of the back of the lower abdomen in front of the lumbar
spine (10).
The skin over the lumbar area is supplied by nerves that come from the roots
of the lumbar spine (10).
A back strain usually occurs when the muscles surrounding the spine are
forced to stretch too far, lift too much weight or move in such a way that they sustain
very small tears. A microscopic amount of bleeding into the muscle usually results
from the tearing of the muscles and ligaments, followed by swelling and muscle
spasms (10).
The actual damage that is done when someone suffers a strained back can
be quite variable. The muscles that support and move the spinal column may be
injured, the ligaments that connect the vertebral bodies together or form strong
capsules around the facet joints might be partially torn or a mild case of a slipped
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intervertebral disc may be the source of the pain. In each of these situations, the
human body is usually able to heal itself and will do so without surgery if given the
proper treatment.
There are many sources of low back pain involving the vertebrae,
intervertebral disks, and nerves. Low back pain caused by soft tissue problems is
likely to originate in one or more of three different locations: 1) Quadratus lumborum
and its adjacent structures. Quadratus lumborum is the muscle between the bottom
rib and the top of the pelvis. It is a key muscle in coordinating upper and lower body
movements. It is a deep muscle, situated underneath the lumbar paraspinal
muscles. Muscle problems are invariably accompanied by connective tissue
problems. This area, unprotected as it is by any skeletal structures, is thick with
connective tissue: the thoracolumbar fascia, the gluteal aponeurosis, and other
tough connective tissue cover and surround these muscles. 2) The buttock muscles.
These include the three gluteal muscles—gluteus maximus, medius and minimus—
and the deep lateral rotators of the hip, especially pyriformis. 3) Iliopsoas. This is the
primary hip flexor—its chief assistant being rectus femoris—running down through
the abdominal cavity and the groin to the lesser trochanter. But its origins are the
inner surface of the ilium (iliacus muscle) and the transverse processes of the
lumbar vertebrae, which mean that every lifting of the leg pulls on the pelvis and the
lumbar spine (11).
2.4. Risk Factors of Low Back Pain
Body measurements and overall posture of the driver, seat/workstation
design, long driving time, long distance driving, duration of employment, social and
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psychological factors and long term whole body and hand-arm vibration exposure
contribute to the development of low back pain.
Anthropometry is the study of human body dimensions. It includes body
volumes, masses of body segments, center of gravity and inertial properties (12).
Engineering anthropometry deals with the application of scientific physical
measurement methods to human subjects for the development of engineering
design standards (13). It includes static and functional measurements of dimensions
and physical characteristics of the body as they occupy space, move and apply
energy to physical objects. Static or structural body dimensions are taken with the
body of the subjects in fixed, standardized positions. Functional or dynamic body
dimensions are taken when the body of the subject is involved in some physical
movement (14).
Anthropometric measurements, such as leg length and weight, are factors to
be included in determining causation of low back pain among bus drivers. Unequal
lengths of both legs might contribute to posture, which if improper might significantly
lead to low back pain. Weight, on the other hand would influence how the spine
would support the body especially the upper back. Anthropometers, tapes and
scales are used to obtain measurement (14).
Another risk factor for LBP is height. It has been suggested that tall people
are at higher risk of having low back pain than short people (15). The average
heights for Filipino adults are as follows: those aged 60 and over, 153 centimeters or
five feet; those aged 40 to 59, 156.2 cm or 5 feet 1 inch; and those aged 20 to 39,
157.6 cm or 5 feet 2 inches. There were significant differences in the average
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heights by sex. Among those aged 20 to 39, the average height for men was 163.3
cm or 5 feet 4 inches (16).
Posture may be a factor causing LBP. It is a position or attitude of the body,
the relative arrangement of body parts for a specific activity, or a characteristic
manner of bearing one’s body (1).
Sitting posture also contributes to the development of low back pain.
Prolonged sitting may result in excessive loading and tissue deformation of the
lumbar spine (17).
The type of sitting posture also plays a role in reducing excessive stresses on
the spine which may lead to LBP. Flexed postures are advantageous, as flexion
results in increased fluid flow and improved transport of nutrients into the
intervertebral discs (18). This may decrease the likelihood of degenerative changes,
which have been associated with decreased metabolic transport in the disc (19).
A similar study also concluded that flexed postures are favorable when sitting
and when lifting heavy materials (20). In a population study on primitive cultures
who squat while sitting in a flexed position, it was found that there was decreased
incidence of degenerative changes in their lumbar spines (21).
On the other hand, a recent study supports the lordotic or extended position
for sitting as beneficial since this posture helps to balance the loads on various
spinal structures and prevents stressing the posterior ligaments (22, 25).
Sitting with the back slouched for as little as 20 minutes can result in
increased laxity of the posterior spinal ligaments. It may take 30 minutes or more for
these ligaments to regain their previous level of stiffness (22). Also, sitting with the
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spine in extension reduces the intradiscal pressure. Extension helps to cause the
nucleus to move anteriorly, thus helping to prevent and reduce the tendency for
posterior disc bulging and protruding (23).
Research has also shown that lumbar disc herniation may result from
prolonged sitting in the typical flexed posture (24).
Lordotic, extended position should be preferred for sitting over the flattened or
flexed posture. However, given that any sitting posture results in increased spinal
loading, frequent changes in posture from sitting to standing, etc., over the course of
a day is to be preferred for protecting the spine (17).
There are several sources of pain in postural problems. The ligaments, facet
capsules, periosteum of the vertebrae, muscles, anterior dura mater, dural sleeves,
epidural areolor adipose tissue and walls of blood vessels are innervated and
responsive in nociceptive stimuli. Also, mechanical stress to pain-sensitive
structures, such as sustained stretch to ligaments or joint capsules or compression
of blood vessels, causes distention or compression of the nerve endings that leads
to the experience of pain. This type of stimulus occurs in the absence of an
inflammation reaction. It is not a pathologic problem but a mechanical one. Relieving
the stress to the pain-sensitive structure relieves the pain stimulus and the person
no longer experiences pain. If the mechanical stresses exceed the supporting
capabilities of the tissues, breakdown will occur. If this continues without adequate
healing, overuse syndromes with inflammation and pain will affect function without
an apparent injury. Relieving the mechanical stress along with decreasing the
inflammation is important (23).
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Pain can come from muscles, ligaments, nerves, discs, or bones. People who
lead a sedentary lifestyle are especially at risk, because their bodies are not
conditioned. They are prone to strains when they use their backs. Other risk factors
include advancing age, frequent or heavy lifting, obesity, poor posture and repetitive
movements including twisting (26).
Seat/workstation design and posture may also be factors in the development
of low back pain. Driving is different from ordinary sitting in that the body is subject
to different forces such as accelerations and decelerations, lateral swaying from side
to side and whole body up and down vibrations while the vehicle is in motion (27).
Prolonged periods of driving in a constrained posture on a seat with poor ergonomic
design during a trip may result in de-conditioning, which is the weakening of the
muscles supporting the spine and trunk due to inactivity, less exercise, and lack of
balance. These muscles cannot fully withstand pressure or even support the spinal
cord to its normal position. Thus, the entire back becomes sore and tired (28).
There is growing evidence that the combination of these factors, coupled with the
design of the seat itself, may increase the risk and occurrence of back problems for
some people.
Ergonomics is an approach, which puts human needs and capabilities at the
focus of designing technological systems. The aim is to ensure that humans and
technology work in complete harmony, with the equipment and tasks aligned to
human characteristics. The term originated from the Greek words “ergon” which
means work and “nomos” which means natural laws (29).
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Ergonomics, also called human factors, is based on biological or natural
sciences. Its main components are anatomy, physiology, psychology, medicine, and
engineering.
The contribution of basic anatomy lies in improving the physical fit between
people and the things they use. Anthropometry provides data on the structure of
human body, in various postures. On the other hand, biomechanics considers body
responses, particularly the operation of muscles and limbs, when subjected to
various internal and external forces. It ensures that working postures are beneficial
and excessive forces are avoided (29).
Human physiology supports two technical areas. Work physiology focuses on
how the body functions when performing work. It addresses the energy
requirements of the body and sets standards for acceptable physical work rate and
workload and for nutrition requirements. Environmental physiology focuses on how
the body functions when subjected to climatological factors. It also includes analysis
of the impact of physical working conditions, such as thermal, noise and vibration,
and lighting, and sets the optimum requirements for these (29).
Psychology is concerned on the behavioral responses of human to work and
environment, particularly human information processing and decision-making
capabilities. It aids in the cognitive fit between people and the things they use (29).
Medicine is directed towards diagnosis of injuries, which can either be acute
or chronic. Lastly, engineering provides information on machinery and assists in its
adaptation for human use (30).
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Ergonomic stressors result from poor workplace designs. These stressors
may include the following: repetition, the number of motions or movements that are
performed per cycle or per shift; force, the power of the muscles used to produce
motion in order to perform necessary activities; and extreme postures, wherein
muscles are required to work at a level near or at their maximum capacity. Before
setting standard measurements and providing necessary seat adjustments,
ergonomic stressors and occurrence of possible health conditions should be
considered (31).
Musculoskeletal disorders are injuries of the soft tissues of the upper
extremities, shoulders and neck, lower back, and lower extremities that are primarily
caused or exacerbated by workplace risk factors, such as sustained and repeated
exertions or awkward postures and manipulations. Repetitive motion injury (RMI),
also known as repetitive stress injury, is a type of stress injury that results from
repetitive motions such as frequent bending or sustained awkward positioning
performed over extended periods of time without allowing for sufficient rest. RMI
includes medical conditions resulting from repeated use of a body part (31).
Ergonomics has a wide application to everyday situations with its significant
implications for efficiency, productivity, safety and health in work settings (29). The
different aspects of the workstation are then evaluated to determine if it fits the
person who works in it.
Workspace is the area within which a person performs the tasks that add up
to one’s job. Its physical design includes working out how much space is needed
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and positioning of furniture, tools, equipment and other items needed to perform
tasks, in respect with posture, access, clearance, reach and vision of the user (32).
The evaluation of the seating of Qantas flight deck crew showed that there is
a widespread postural discomfort due to insufficient room space and LBP during
flying among middle- and long-distance Qantas pilots (33). It was also found that an
unsuitable workspace that prevents employees from sitting in a balanced position
can cause poor body positions. The physical arrangement of work space elements
such as work surfaces, tools and equipment may not correspond with the reaches
and clearances of seated employees. The workstation may also be unsuitable
because the seats are too high or low for an employee's body size and shape.
These changes may ultimately lead to low back pain (34).
The ergonomic design of the driver’s workstation is a necessary component
of driver safety and health protection. The relative comfort and functional utility of
the driver’s seat is a consequence of their physical design in relation to the physical
structure and biomechanics of the human body (35).
The driver’s seat should be vertically and horizontally adjustable and have
adjustable lower back support and springs (36).
The height of the seat should be such as to avoid excessive pressure on the
thigh. The front edge of the seat should be a bit lower than the distance from the
floor to the thigh, when seated. It was recommended that the front edge be at least
2 inches below the popliteal crease, which is the crease at the back of the hollow
knee (37). The length and width of the seat would partly depend on the type of seat.
In general, the length should be set to be suitable for small persons in order to
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provide clearance for the calf of the leg and to minimize thigh pressure, and the
width should be set to be suitable for large persons (14).
The steering wheel should be adjustable along the axis of the steering
column. Possible adjustments in its angle of inclination can provide more comfort.
The pedals should have equal angles and be within easy reach for both short and
tall drivers (36).
The measurements of the workstation and the adjustments that can be made
should fall within a range that is applicable to all drivers. The adjustability and the
ways of adjusting the driver’s seat and steering wheel should be coordinated so
drivers within the design range can find positions for their arms and legs that are
comfortable and ergonomically healthy.
Seats should provide for correct curvature of the lumbo-sacral section of the
spine in order to keep the spinal column in a state of balance. Seats without or with
inadequate backrest may cause kyphosis, a forward-leaning posture produced by
excessive pressure between the vertebrae. The lordosis type of posture with
adequate lumbo-sacral back support represents a more desirable posture. An angle
of 90 degrees or less between the seat pan and backrest may cause pressure on
the lower lumbar discs and back muscles. The resultant forces contribute to LBP
and degeneration of the lumbar spine (14). Loss of rigidity and sagging of the seat
pan due to wear and tear results in elevation of the knee to a higher level which
causes gravity forces of the upper body to concentrate at the lower lumbar spine.
The seat surface should be more or less plane rather than shaped, although a
rounded front edge is highly desirable. Upholstery should be firm rather than soft.
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The covering materials should also be porous for ventilation and rough to aid
stability (38).
In order to establish a desirable posture, the angle of the seat and back
should be considered. The seat should be at a moderate angle and the back should
have an angle of from about 95 to 105 degrees or more with the seat. With
inclination of the backrest to at least 20 degrees, the amount of support needed to
balance the trunk is minimized and body weight is transferred to the backrest.
Adequate support for the lumbar area should also be taken into consideration. It is
important in preventing spinal complications and discomfort caused by angles
between the vertebrae (14).
A probable solution to LBP due to poor posture is the use of a lumbar pad
support. A study in the Philippines showed that use of lumbar pad support
significantly decreased the occurrence of LBP among taxi drivers. Thirty taxi drivers
with LBP due to poor posture were asked to use the pad support. The occurrence of
LBP among them was compared with a similar sample size not using lumbar pad
support (39). Lumbar pad supports can compensate for an ineffective postural seat
design which may contribute to tension and fatigue of driver.
Foot posture contributes to development of low back pain in that poor foot
posture can affect the ligaments of the lower limb and put more stress on the back
and knees. Driving involves active use of the feet—the right foot on the accelerator
pedal, the left on the brake and also on the clutch in a stick shift. When the feet are
active, they cannot be used to support and stabilize the lower body unlike ordinary
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sitting wherein the feet are rested on the floor. Poor quality or worn footwear do not
properly support the feet as well (40).
Long driving time refers to the length of time the driver spends at the wheel
while traveling. Continuous driving for four hours or more can increase the risk of
having low back pain. Driving with limited movements for a prolonged period or
sitting in one position for hours can aggravate back pain and even damage one’s
health because of fatigue and lack of exercise (41). A study found that after
accounting for all the possible psychological causes of back injury, drivers with the
San Francisco Municipal Railway (Muni) still have an elevated risk for injury that can
be attributed solely to their physical working conditions, particularly the number of
hours on the job. Drivers who worked full-time had more than twice as many back
injuries as those who worked part time (42).
Driving distance pertains to the interval, in kilometers, between the origin and
destination. Men drive an average of 71 kilometers and women 55 kilometers each
day (27). Long driving distance is applicable to buses, which travel from urban to
rural areas, and vice versa.
The duration of employment is the span of time or number of years a person
has been engaging his services as a driver of a company. This factor usually goes
with age. Young drivers have more acute episodes of back pain while older people
have more cases of chronic pain (43). High-risk occupations such as those with
exposure to whole body vibration caused by long distance driving, place workers at
risk for low back pain. The longer a person is on the job, the higher the risk (41).
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Epidemiologic studies on low back pain consistently show a strong correlation
with whole body vibration from motor vehicle driving (44). Other sources of vibration
may include rocky and bumpy roads, worn out shock absorbers and bus engines
that are not well-maintained. Vehicle vibration enters the driver's body through the
seat. The structural properties of automobile seats may be a source of LBP for the
driver. Because of the strong coupling between the seat backrest and the vehicle
floor, a differential motion between backrest and seat cushion occurs when driving. It
inevitably induces continuous strains in the lower lumbar spine of the seat occupant
and is therefore a possible source of low back pain (45).
Two general categories of vibration impinging on humans are whole body
vibration or WBV (vibration transmitted to the entire body through some support
such as a vehicular seat or building floor); and segmental (e.g. hand-arm) vibration
(vibration locally applied to specific body parts such as hands and arms from a
vibrating hand tool). Bus drivers, among others, are exposed to both types of
vibration. The vehicle moving and hand-arm vibration cause whole body vibration by
contact with the gear stick when shifting gears (46).
A British study found exposure to hand-transmitted vibration and finger
blanching and sensory symptoms to be significantly associated. There was no
marked excess of LBP complaints in workers exposed to WBV, with only moderate
excesses in men exposed above the British Standard and male riders of heavy
industrial vehicles (47).
Whole body vibration exposure is another risk factor for low back pain. In a
questionnaire survey of back pain symptoms in professional truck drivers, three
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factors were found to be related significantly to the prevalence of LBP. These were
irregular duty time, short resting time and long driving time in a day (9). Evidence
also shows that while LBP is age-related, it is also occurring earlier than expected
for workers exposed to whole body vibration (48). Whole body vibration is related to
prolonged sitting posture, poor working posture and inadequate working conditions
in contributing to low back pain (49).
A number of studies have been conducted on the association of vibration
exposure and low back pain. It was found that the occurrence of low back
symptoms increased with increasing whole body vibration exposure in terms of total
or lifetime vibration dose, equivalent vibration magnitude and duration of exposure
from years of service. Frequent awkward exposures are also related to some types
of low back symptoms. Moreover, risk may be due to both whole body vibration
exposure and prolonged sitting in a constrained posture (50). However, it was
determined that in many working situations with a daily exposure of eight hours or
more, suspension seats—conventional or air—will not protect drivers from harmful
exposure to whole body vibration (51).
To measure the level of exposure quantitatively, a vibration signal is first
collected using vibration pickup devices, which are usually placed on machinery
bearing caps. The caps are an ideal place for pick-ups because of their accessibility
and because they are the points through which vibration transmits the most readily.
For each point, the vibration signal picked up is then recorded in a vibration meter or
vibration analyzer. A vibration meter will allow defect determination, but to analyze
the cause, a vibration analyzer is needed (52).
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Psychological factors play a role in the three phases of LBP—onset of pain,
perception of pain and chronic pain. Recent research shows that in many people,
preexisting depression and the inability to cope may be more likely to predict the
onset of pain than physical abnormalities. Moreover, social and psychological
factors play a part in the severity of pain a person experiences. Depressed people
are more likely to experience vague physical symptoms, including LBP. In a study of
truck and bus drivers, almost all the truck drivers liked their work and their bosses
while bus drivers stated much lower job satisfaction. 50% of the truck drivers
reported LBP but only 24% lost time at work. Bus drivers with LBP had a significantly
higher absentee rate in spite of less stress on their backs. A related study found that
pilots who generally reported high job satisfaction reported much fewer back
problems than their flight crews. Another study stated that low rank, low social
support and high stress in soldiers were associated with a higher risk for disabling
back pain. Also, the way a patient perceives and copes with pain at the beginning of
an acute attack may in fact condition the patient to either recover or develop a
chronic condition. Those who over-respond to pain tends to feel out of control and
discouraged, increasing their risk for long-term problems. A study found that among
patients with back problems, the fear of pain was actually more disabling than the
pain itself (53).
Depression, low activity or high pain behavior, negative beliefs or fear of pain
are three psychological-behavioral factors that consistently show a significant
relationship with LBP. However, it has not been determined which of these factors is
greatly involved in predicting disabling LBP (54).
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Emotional factors which increase experienced pain include anxiety, anger and
depression. Specific psychological factors that can increase pain are degree of focus
on the pain, boredom, beliefs about the meaning of the pain and a sense of poor
control over pain (55).
Psychological factors are important in people with chronic low back pain.
Dissatisfaction with a work situation, the management, or a job and boredom
contribute significantly to the onset and persistence of LBP (56).
The research on Muni drivers, led by Niklas Krause, showed that physical and
psychosocial conditions in the workplace play a role in causing back injury. The
research also found that after accounting for physical work load, a stressful job with
high psychological demands, low satisfaction and low supervisor support can cause
spinal injury (42).
There are many other factors not related to driving which should also be
considered in LBP. For ages 20-60, a herniated disc may be the cause of LBP.
Other possible causes are myofascial pain, spondylolysis, fracture, facet syndrome,
stenosis, fibromyalgia, infection, spondyloarthropathy, and tumor (57).
LBP can also be caused by referred pain. Referred pain is pain caused by
one part of the body and is also perceived in another distant part of the body not
directly involved with the cause. Most common sources of referred pain to the low
back are the organs in the abdomen, pelvis and retroperitoneal space, such as
stomach, intestines, uterus and ovaries and kidneys. For example, pain of peptic
ulcer, diverticulitis of the colon, pelvic inflammatory disease, acute prostates and
22
trochanteric bursitis (inflammation of the bursa of the hip area) can refer pain to the
low back (58).
Low back pain is a persistent global problem and everyone is susceptible. Its
prevalence is consistently similar across countries. It has been studied extensively
and has been shown to be possibly be prevented with the right measures. Still, the
problem remains unsolved.
In the Philippines, no studies have been done on LBP among bus drivers.
Several studies have been done on LBP, but of different population other than bus
drivers. This study would contribute to the pool of knowledge already available
regarding LBP status in the Philippines and possibly that of Southeast Asia.
Preventive measures may be designed in order to address the current situation of
the LBP among Filipino male bus drivers.
3.0 Objectives of the Study
General Objective: To identify risk factors associated with low back pain among bus
drivers.
Specific Objectives:
1. Describe the distribution of bus drivers according to age, long driving time,
vibration exposure, long distance driving, driving posture, seat/workplace
design and psychological factors.
2. Describe the distribution of bus drivers with low back pain by age, long driving
time, vibration exposure, long distance driving, driving posture,
seat/workplace design and psychosocial aspects.
23
3. Determine the risk factors of low back pain adjusting for the effects of
confounders.
4.0 Significance of the Study
Studies in the Western countries have shown that vehicle drivers—trucks,
buses, taxis—are at an increased risk of developing low back pain, with contributing
factors such as long driving time, whole body vibration exposure, long distance
driving, ergonomics, age, duration of employment and psychological factors.
However, there are no known studies conducted in the Philippines to look into the
effects of these factors to the development of low back pain among Filipino bus
drivers.
This study will determine if an association exists between the risk factors and
low back pain among Filipino bus drivers. Driving would expose the drivers to long
periods of experiencing vibration, poor ergonomic conditions, long distance travel
and long driving time, causing low back pain. Necessary measures can then be
recommended that will alleviate and/or prevent low back pain, which would benefit
the bus drivers in terms of better health as well as the companies in terms of
increased productivity.
24
25
6.0 Materials and Methods
6.1 Study Design
An analytical cross-sectional study was done in 8 bus companies
located along Gil Puyat Avenue and Epifanio delos Santos Avenue at Pasay
City. Preliminary visits and discussion with managers were performed in
order to gather preliminary data on the feasibility of the study and to ask initial
permission to be able to implement the study.
6.2 Study Population
The study included as its subjects Filipino male air-conditioned bus
drivers from 8 bus stations. Non-airconditioned bus drivers were not included
in order to maintain the homogeneity of the subjects. Also, according to the
bus company managers, air-conditioned bus drivers more often complain
about low back pain (LBP) than non-airconditioned bus drivers and therefore,
it is expected to have more cases of LBP.
Several studies in other countries have shown a low back pain
prevalence of about 50% (9). Initial interviews with the bus drivers and
supervisors also showed that LBP is a common medical complaint of drivers.
Based on these, the sample size was computed as follows:
P = 0.5662 α or d = 0.05 Z α = 1.96 Q = 1- P n = PQZ2
d2
P = proportion of bus drivers with chronic low back pain Q = 1 – P Z = normal variate Z α = 1.96 where α = 0.05
α = maximum allowable error
26
n = 0.5662 x 0.4338 x (1.96) 2
(0.05) 2
n = 377.4 = 378 subjects
Proportional allocation was done to assure proper presentation of each
bus company in the study. Using the formula Pax = ( n1 / T) x n, the number
of subjects per bus station was computed as follows:
where:
Pax = proportionally allocated sample size per bus (x1, x2,…,xn)
company
n1 = total number of drivers per company
T = total number of bus drivers from all the companies
n = computed sample size
n = Pax1 + Pax2 + … + Pax10
The following were the computed proportionally allocated sample size per bus
station:
• Tritran Bus Company – 31
• Grand Star Coach Bus Company – 8
• Green Star Bus Company – 51
• JAC Liner – 4
• BBL Transportation Systems Inc. – 16
• Victory Liner – 75
• Pangasinan Five Star Bus Company, Inc. – 118
• Philtranco – 74
27
6.3 Data Collection
The group sent a letter to each bus company management, which
stated the objectives of the study and asked for their permission to allow their
company to be included in the study. The group also verified the initial data
about the number of drivers employed in each company.
The researchers went to the bus stations everyday for three weeks,
depending on a schedule, which was prepared, based on the availability of
drivers. Drivers were approached while they were taking a break or waiting
for their buses to get full. The information and consent form was given for
signature and a self-administered questionnaire was given to each driver
afterwards. A group member (S1) provided assistance and answered queries
from drivers when necessary. In addition, the same student quickly edited
accomplished questionnaires. While the questionnaires were being
answered, the corresponding bus and bus seat/workplace dimensions were
measured by two other members (S3 and S4) of the group. The subjects
were also asked to show their usual driving posture by sitting on the bus
driver’s seat. Leg reach to the pedal, arm reach to the steering wheel and
reclining angle were measured. Anthropometric measurements (leg length,
arm length and weight) were measured by another member of the group (S2)
after the subjects have finished answering the questionnaires assisted by S1.
Exposure of the drivers to vibration was measured qualitatively using the
questionnaire.
28
6.4 Data Collection Tools
Assisted Self-Administered Questionnaire
This was used to determine demographic data and information
about driving time, driving distance, driving posture, duration of
employment as a driver and psychosocial factors.
Measuring Tape
Leg length, arm length and seat / workstation dimensions were
taken using a measuring tape. This data was important to relate body
posture and seat design in relation to LBP.
Protractor
This was used to measure the reclining angle of the seat.
Weighing Scale
This was used to estimate the subject’s weight. This data was
important since it had an effect on the force exerted on the lower back
when the person is sitting or standing.
6.5 Data Processing
From the data gathered, a coding manual was prepared. Data was
encoded using Epi-Info Software version 6.0 and Statistical Package for
Social Sciences (SPSS) version 10.0 available in the group’s personal
computer. These data were processed into tables and graphs for better
visual analysis.
29
6.6 Data Analysis
The risk factors included were vibration exposure, rough roads, long
driving time, long distance driving, uncomfortable sitting posture, insufficient
room space, constrained driving posture, seat design and psychological
factors. The prevalence of LBP among the subjects was also computed. Chi
square test and logistic regression were used to test for the association of risk
factors and low back pain. Finally, multivariate analysis was performed with
the use of SPSS using backward-Wald method.
6.7 Operational Definition of Variables
Dependent variable:
1. Low Back Pain – chronic pain localized in the lumbo-sacral spine with
an acute and sudden onset lasting for about thirty minutes and is
intermittent and recurring for at least six months.
Independent variables:
1. Long Distance Driving – driving distances wherein low back pain is felt
2. Long Driving Time – driving for more than four hours everyday
according to a study on bus drivers in Lithuania
30
3. Duration of employment – this is the span of time (number of months
and years) a person has been engaging his services as a bus driver.
4. Posture – a position of attitude of the body, the relative arrangement of
body parts while driving which includes reclining angle, sitting, arm,
and leg position
5. Psychological Factors – depression, low activity or high pain behavior,
negative belief, or fear of pain
6. Depression – feeling down or unhappy with working conditions or
family problems related to mental stress
7. Boredom – state of being uninterested because of frequent exposure
to long hours of driving
8. Constrained posture – inability to maintain a comfortable sitting
position while driving
9. Abnormal vibration – unusual vibration due to poorly maintained buses
10. Vibration exposure – exposure to vibration for more than 4 hours a
day, abnormal vibration complaint, with at least 20% rough roads
experienced
Confounding variables:
1. Seat / workstation Design – the overall make-up of the drivers’ seat in
relation to easing low back pain and other injuries which include the
reclining angle of back seat and overall adjustability
2. Age – number of years lived of subject since last birthday.
31
Other definitions:
1. Pain – unpleasant sensory experience associated with actual negative
potential tissue damage or described in terms of such damage.
2. Anthropometry – dealing with measurement of leg length, arm length,
and weight
3. Work – an activity in which one exerts strength or faculties to do or
perform a labor, task, or duty that affords ones accustomed means of
livelihood
7.0 Ethical Considerations
An informed consent form was prepared which explained all the information
about the study and was signed by each participant. Any information obtained
from the drivers employed in the different bus companies were kept confidential.
The study is not obliged to provide treatment for identified cases of low back pain
(LBP). Instead, any form of intervention will remain as the bus companies’
responsibility upon giving them the results of the study.
8.0 Assumptions, Strengths and Limitations
This study presupposed that all answers to the questions provided to bus
drivers are truthful and reliable.
The strength of this study is related to the fact that no similar studies
locally have been done in the past. The results of the study can serve as basis
for future researches among bus drivers in a larger scale. In addition, aside from
32
presenting low back pain among bus drivers, companies will also benefit in terms
of less worker absence and improved productivity once low back pain complaints
are reduced.
Only air-conditioned bus drivers were included in the study. Simple
random sampling was not done in the selection of the bus drivers for reasons
that their schedules are not fixed and they usually are on a rotation basis.
Drivers also come at different times and based on the limited time available for
data collection, waiting for the driver based on the selection by random sampling
will not allow fulfillment of the sample size required. The subject’s availability
during the scheduled visits of the researchers and willingness to participate were
instead used as criteria for participation. A great degree of selection bias was not
expected since the bus drivers were informed that no treatment would be
provided if found with low back pain. Thus, drivers with low back pain were not
expected to volunteer which will unduly increase the number of LBP cases. In
addition, personal characteristics and risk factors were elicited which were
controlled for in the data analysis using logistic regression. Vibration exposure
was measured qualitatively using a questionnaire due to the unavailability of a
vibration meter for a quantitative measurement. However, the study attempted to
put together several risk factors affecting exposure to vibration such as seat
design and exposure to rough roads.
Based on the recommendation of the study’s ergonomics adviser,
quantitative analysis of anthropometric and ergonomic data cannot be performed
33
due to limitations of time and data gathered. However, these data will be kept
for future use in related studies.
9.0 Results and Discussion
After data collection, the data were presented based on univariate, bivariate
and multivariate analysis.
9.1 Univariate Analysis
Figure 1. Civil Status of Subjects
4%
Single1%95% Married
0% Separated Widowed 95% of the drivers are married. Table 1. Insufficient workspace experience
Insufficient workspace Frequency Percentage No 143 37.8 Yes 235 62.2
A little over 60% of the drivers complained of experiencing insufficient workspace. Figure 2. Abnormal vibration
81%
19%YesNo
81% of the drivers experienced abnormal vibration due to their current job.
Table 2. Uncomfortable sitting posture Uncomfortable sitting posture Frequency Percentage
No 145 38.4 Yes 233 61.6
A little over 60% of the drivers experienced uncomfortable sitting posture at their workstation.
34
Figure 3. Constrained posture
68%
32%
YesNo
Nearly 70% of the drivers had constrained posture at the workstation. Table 3. Rough roads
Rough roads Frequency Percentage No 20 5.3 Yes 358 94.7
Almost 95% of the drivers experienced rough roads while driving. Figure 4. Boredom
74%
26%
YesNo
74% of the drivers experienced boredom while driving. Table 4. Depression
Depression Frequency Percentage No 154 40.7 Yes 224 59.3
Nearly 60% of the drivers had experienced depression. Figure 5. Frequent movement of back
92%
8% YesNo
A little over 90% of the drivers move their backs frequently while driving. Table 5. Frequent movement of arms
Frequent movement of arms Frequency Percentage No 36 9.5 Yes 342 90.5
Almost 91% of the drivers frequently move their arms while driving.
35
Figure 6. Frequent movement of shoulders
96%
4% YesNo
96% of the drivers frequently move their shoulders while driving. Table 6. Frequent movement of feet
Frequent movement of feet Frequency Percentage No 31 8.2 Yes 347 91.8
92% of the drivers frequently move their feet while driving. Figure 7. Back pain experience 14% Yes
No 86%
86% of the drivers experienced back pain. Table 7. Upper back pain experience
Upper back pain Frequency Percentage No 256 67.7 Yes 122 32.3
32% of the drivers experienced upper back pain. This comprises about 37% of all back pain complaints. Table 8. Mid back pain experience
Mid back pain Frequency Percentage No 318 84.1 Yes 60 15.9
16% of the drivers experienced mid back pain. This comprises almost 20% of all back pain complaints. Table 9. Low back pain experience
Low back pain Frequency Percentage No 120 31.7 Yes 258 68.3
68% of the subjects experienced low back pain. This comprises almost 80% of all back pain complaints.
36
99% 1% YesNo
Figure 8. Rest period Almost all of the drivers have rest periods in between trips. Table 18. Work Satisfaction
Work Satisfaction Level Number Percentage I like my job 334 88.4
Just right 44 11.6 I don’t like my job 0 0
Others 0 0 All of the drivers are satisfied with their work. Figure 9. Employee satisfaction with management
27%
50%
13%
10%I Am HappyI LikeI Don't LikeI Am not Happy
A little over 75% of the drivers are satisfied with management. Table 11. Relationship with co-workers
Relationship Number Percentage Good 313 82.8
Just right 63 16.7 Difficult 1 0.3 Others 1 0.3
Almost all have good relationship with co-workers.
16%54%
20%
10% HappyEnoughNot EnoughNot Happy
Figure 10. Salary satisfaction
70% of the drivers are satisfied with their salaries.
37
Table 12. Seat design Type of Seat Design Frequency Percentage
With cushion and with lumbar pad support 292 77.2 With cushion but without lumbar pad support 83 22 Without cushion but with lumbar pad support 0 0
Without cushion and without lumbar pad support 0 0 Others 3 0.8
Almost 80% of the driver seats are cushioned and have lumbar pad supports. Figure 11. Driving posture
45%
47%8% Reclined
StraightStooped
45% of the drivers have reclined driving posture. 47% have straight posture while driving. Only about 10% have stooped driving posture. Table 13. Seat reclinability
Reclinability Frequency Percentage No 175 36.3 yes 203 53.7
Almost 55% of the driver seats can be reclined. Figure 12. BMI
1%
36%
52%11%
Underweight (< 18.5)
Healthy Weight (18.5-24.9)
Overweight (25-30)
Obese (>30)
A little over 60% of the drivers exceeded the normal BMI. Only 36% met the normal BMI.
38
Table 14. Age Group Age group Frequency Percentage
20-24 49 13 25-29 60 15.9 30-34 45 11.9 35-39 70 18.5 40-44 70 18.5 45-49 58 15.3 50-54 20 5.3 ≥ 55 6 1.6
A little over 90% of the drivers are aged 20-49. The age group 35-44 comprises almost 40% of the drivers. Table 15. Number of years employed
Number of years Frequency Percentage 0-4 32 8.5 5-9 62 21.7
10-14 172 45.5 15-19 29 7.7 20-24 30 7.9 25-29 21 5.6 > 30 12 3.2
45% of the drivers have been employed for 10-14 years as bus drivers.
4%
7%
19%
41%
24%
3%
2%
100-199 200-299
300-399 400-499
500-599 600-699
> 700
Figure 13. Long distance driving 42% of the drivers drive from 400-499 kilometers per day. Figure 14. Vibration Exposure 35%
Yes No
65% 65% of the drivers are exposed to vibration while driving.
39
Table 16. Long driving time Hours Frequency Percentage
< 8 15 4 9-10 28 7.4 11-12 124 32.6 13-14 84 22.2 15-16 61 16.1 17-18 39 10.3 ≥ 19 27 7.1
A little over 30% of the drivers drive from 11-12 hours per day while 56% drive at least 13 hours per day. Table 17. Frequency of low back pain in a day in hours
Hours Frequency Percentage < 0.5 126 33.3 0.5-5 195 51.6 6-10 26 6.9 > 10 31 8.2
A little over 50% of the drivers experience LBP from 30 minutes to 5 hours a day. Table 18. Frequency of LBP in a week Frequency of Low Back Pain
in days per week Number Percentage
1-2 249 65.9 3-4 54 14.3 5-7 75 19.8
About 65% of the drivers experience LBP once to twice a week.
33%9%
13%
13%
10% 6%
2%
9%
5%
0 > 0 - < 1
1-1.99 2-3.99
4-5.99 6-7.99
8-9.99 10-11.99
> 12
Figure 15. Duration of LBP experience in years
36% of the drivers have experienced LBP from one to less than six years. A little over 30% did not experience LBP at all. Table 19. LBP cases
Cases of LBP Number Percentage No 144 38.1 Yes 234 61.9
A little over 60% of drivers have LBP.
40
Figure 16. Rough roads experienced
27%34%
18% 9%12%
< 20 20-39
40-59 60-79
> 80
A little over 60% of the drivers experience less than or equal to 39% of rough
roads. Table 20. Weight
Kilograms Frequency Percentage 45-54 8 2.1 55-64 59 15.6 65-74 138 36.5 75-84 120 31.7 85-94 38 10.1 > 95 15 4
Almost 70% of the drivers weigh from 65-84 kilograms. Table 21. Height
Centimeters Frequency Percentage < 159 27 7.1
160-160.9 18 4.8 161-161.9 16 4.2 162-162.9 16 4.2 163-163.9 28 7.4 164-164.9 15 4 165-165.9 23 6.1 166-166.9 15 4 167-167.9 28 7.4 168-168.9 34 9 169-169.9 17 4.5 170-170.9 26 6.9 171-171.9 21 5.6 172-172.9 12 3.2 173-173.9 23 5.1 174-174.9 11 2.9
> 175 48 12.7 Almost 30% of the drivers have heights from 167 to less than 171 centimeters.
41
Figure 17. Seat reclining degree
3%
31%
31%
6% 16%
7%
6%
< 95 95-97
98-100 101-103
104-106 107-109
> 110
About 60% of the seats are reclined from 95 to 100 degrees. Table 22. Number of buses driven out of 10 buses with adjustable seats toward and away from the wheel
Number of buses Frequency Percentage 0-1 32 8.5 2-3 18 4.8 4-5 19 5 6-7 9 2.4 8-9 36 9.5 10 264 69.8
Almost 10% of the drivers have driven buses without adjustable seats. Table 23. Number of buses driven out of 10 buses with reclinable seats
Number of buses Frequency Percentage 0-1 126 33.3 2-3 17 4.5 4-5 20 5.9 6-7 10 2.6 8-9 31 8.2 10 174 46
A little over 33% of the drivers have driven buses without reclinable seats.
42
9.2 Bivariate Analysis
A. Results
Pearson chi square test was used to determine the association of risk factors
with low back pain. Significant associations were based on a 5% level. A p-value cut
off of ≤ 0.2 was used for all independent variables which will subsequently be
included in the multivariate analysis. A summary of the results of the Pearson chi
square test for association is shown below.
Table 24-A. Summary of Variables Cross-Tabulated with LBP Using Chi Square Test for Association with P value of ≤ 0.2
Association between
Independent variable Dependent Variable
Chi square
P value Remarks
1. Constrained posture LBP 24.89 0.000 Significant Association 2. Uncomfortable sitting posture LBP 11.05 0.001 Significant Association 3. Frequent movement of shoulders
LBP 8.08 0.004 Significant Association
4. Long distance driving LBP 16.59 0.011 Significant Association 5. Boredom LBP 6.04 0.014 Significant Association 6. Depression LBP 5.45 0.020 Significant Association 7. Insufficient work space LBP 5.18 0.023 Significant Association 8. Long driving time LBP 4.229 0.040 Significant association 9. Abnormal vibration LBP 4.08 0.043 Significant Association 10. Frequent movement of back
LBP 3.95 0.047 Significant Association
11. Employee satisfaction with management
LBP 6.02 0.110 No Significant Association
12. Height LBP 21.80 0.150 No Significant Association 13. Percent of rough roads LBP 6.67 0.154 No Significant Association 14. Vibration exposure LBP 1.91 0.167 No Significant Association 15. Rough roads LBP 1.86 0.173 No Significant Association
Table 24-B. Summary of Variables Cross-Tabulated with LBP Using Chi Square Test for Association with P value of > 0.2
Association between
Independent Variable Dependent Variable
Chi square
P value Remarks
1. Years of education LBP 0.93 0.335 No Significant Association 2. Consultation with doctor after injury
LBP 2.18 0.337 No Significant Association
43
3. Injury to right shoulder LBP 2.18 0.337 No Significant Association 4. Injury to both arms LBP 2.18 0.337 No Significant Association 5. Seat base length LBP 10.05 0.346 No Significant Association 6. Duration of employment LBP 6.44 0.375 No Significant Association 7. Injury to right foot LBP 1.88 0.391 No Significant Association 8. Accident experienced LBP 0.65 0.419 No Significant Association 9. Salary satisfaction LBP 2.67 0.445 No Significant Association 10. Accident injury LBP 1.47 0.479 No Significant Association 11. Frequent movement of arm LBP 0.42 0.519 No Significant Association 12. Injury to left leg LBP 1.24 0.537 No Significant Association 13. Sprain LBP 1.24 0.537 No Significant Association 14. Civil status LBP 2.06 0.559 No Significant Association 15. Seat adjustability towards and away from the steering wheel
LBP 0.34 0.559 No Significant Association
16. Job training LBP 0.32 0.570 No Significant Association 17. Length of training for current job
LBP 3.76 0.585 No Significant Association
18. Type of seat LBP 0.22 0.63 No Significant Association 19. Self training LBP 0.89 0.641 No Significant Association 20. Injury to chest LBP 0.68 0.712 No Significant Association 21. Injury to back LBP 0.68 0.712 No Significant Association 22. Injury to right thigh LBP 0.68 0.712 No Significant Association 23. Reclining degree of seat LBP 3.68 0.720 No Significant Association 24. Weight LBP 2.86 0.721 No Significant Association 25. Relationship with co- workers
LBP 1.3 0.729 No Significant Association
26. Training from current job LBP 0.6 0.742 No Significant Association 27. Body mass index LBP 1.08 0.783 No Significant Association 28. Frequent movement of feet LBP 0.07 0.790 No Significant Association 29. Work satisfaction LBP 0.06 0.800 No Significant Association 30. Inclination of seat LBP 0.06 0.804 No Significant Association 31. Training from previous job LBP 0.41 0.815 No Significant Association 32. Driving position LBP 0.37 0.830 No Significant Association 33. Injury to left arm LBP 0.33 0.847 No Significant Association 34. Injury to both shoulders LBP 0.03 0.859 No Significant Association 35. Injury to left thigh LBP 0.03 0.859 No Significant Association 36. Injury to both thighs LBP 0.33 0.859 No Significant Association 37. Injury to right knee LBP 0.03 0.859 No Significant Association 38. Injury to left knee LBP 0.03 0.859 No Significant Association 39. Injury to both knees LBP 0.33 0.859 No Significant Association 40. Injury to right leg LBP 0.03 0.859 No Significant Association 41. Injury to both legs LBP 0.03 0.859 No Significant Association 42. Injury to left foot LBP 0.33 0.859 No Significant Association 43. Injury to both feet LBP 0.03 0.859 No Significant Association 44. Dislocation LBP 0.03 0.859 No Significant Association 45. Muscle strain LBP 0.03 0.859 No Significant Association 46. Fracture LBP 0.29 0.864 No Significant Association 47. Injury to right arm LBP 0.18 0.913 No Significant Association 48. Age LBP 1.97 0.962 No Significant Association 49. Number of buses out of 10 buses with reclining seats
LBP 0.61 0.988 No Significant Association
44
Fifteen independent variables cross-tabulated with LBP were found to have a
p-value of ≤ 0.2 using Chi square test for association. These were, constrained
posture, abnormal vibration, vibration exposure, uncomfortable sitting posture,
boredom, depression, frequent movement of back, frequent movement of shoulders,
long distance driving, long driving time, insufficient workspace, employee satisfaction
with management, percent of rough roads, rough road experience and height.
Variables with a p-value of ≤ 0.2 were included for purposes of logistic regression
analysis. The following are the cross tabulations of the independent variables with
LBP.
Table 25. Relationship of Insufficient Work Space and LBP Insufficient Work Space Low Back Pain
No Yes Frequency Percentage Frequency Percentage
No 65 45.8 77 54.2 Yes 79 33.5 157 66.8
Chi square = 5.18 P value = 0.02287480 There is a significant relationship between insufficient room space and LBP. Table 26. Relationship of Abnormal Vibration and LBP
Abnormal Vibration Low Back Pain No Yes Frequency Percentage Frequency Percentage
No 35 49.3 36 50.7 Yes 109 35.5 198 64.5
Chi square = 4.08 P value = 0.04328993 There is a significant relationship between abnormal vibration and LBP. Table 27. Relationship of Uncomfortable Sitting Posture and LBP Uncomfortable Sitting Posture Low Back Pain
No Yes Frequency Percentage Frequency Percentage
No 71 49.0 74 51 Yes 73 31.3 160 68.7
Chi square = 11.05 P value = 0.00088653 There is a significant relationship between uncomfortable sitting posture and LBP.
45
Table 28. Relationship of Constrained Posture and LBP Constrained Posture Low Back Pain
No Yes Frequency Percentage Frequency Percentage
No 69 56.6.0 53 43.4 Yes 75 29.3 181 70.7
Chi square = 24.89 P value = 0.00000061 There is a significant relationship between constrained posture and LBP. Table 29. Relationship of Rough Roads and LBP
Rough Roads Low Back Pain No Yes Frequency Percentage Frequency Percentage
No 11 55.0 9 45 Yes 133 37.2 225 62.8
Chi square = 1.86 P value = 0.17285062 There is no significant relationship between rough roads and LBP. Table 30. Relationship of Percent of Rough Roads and LBP
Percent Low Back Pain No Yes Frequency Percentage Frequency Percentage
<20 45 43.7 58 56.3 20-39 45 35.2 83 64.8 40-59 24 35.8 43 64.2 60-79 17 51.5 16 48.5 ≥80 13 27.7 34 72.3 Chi square = 6.67 P value = 0.15420584 There is no significant relationship between percent of rough roads traveled and LBP. Table 31. Relationship of Boredom and LBP
Boredom Low Back Pain No Yes Frequency Percentage Frequency Percentage
No 48 49.0 50 51.0 Yes 96 34.3 184 65.7
Chi square = 6.04 P value = 0.01400367 There is a significant relationship between boredom and LBP.
46
Table 32. Relationship of Depression and LBP Depression Low Back Pain
No Yes Frequency Percentage Frequency Percentage
No 70 45.5 84 54.5 Yes 74 33.0 150 67.0
Chi square = 5.45 P value = 0.01953236 There is a significant relationship between depression and LBP. Table 33. Relationship of Frequent Movement of Back and LBP
Movement of Back Low Back Pain No Yes Frequency Percentage Frequency Percentage
No 17 56.7 13 43.3 Yes 127 36.5 221 63.5
Chi square = 3.95 P value = 0.04690682 There is a significant relationship between frequent movement of back and LBP. Table 34. Relationship of Frequent Movement of Shoulders and LBP
Movement of shoulders Low Back Pain No Yes Frequency Percentage Frequency Percentage
No 12 75.0 4 25.0 Yes 132 36.5 230 63.5
Chi square = 8.08 P value = 0.00446599 There is a significant relationship between frequent movement of shoulders and LBP. Table 35. Relationship of Long Driving Time and LBP
Number of hours driven Low Back Pain No Yes Frequency Percentage Frequency Percentage
< 8 9 64.3 5 35.7 > 8 135 37.1 229 62.9 Chi square = 4.229 P value = 0.040 There is a significant relationship between long driving time and LBP.
47
Table 36. Relationship of Long Distance Driving and LBP Distance (in kilometers) driven Low Back Pain
No Yes Frequency Percentage Frequency Percentage
100-199 9 64.3 5 35.7 200-299 15 53.6 13 46.4 300-399 25 35.7 45 64.3 400-499 52 33.1 105 66.9 500-599 40 44.9 49 55.1 600-699 3 27.3 8 72.7 ≥700 0 0 9 100 Chi square = 16.59 P value = 0.01093037 There is a significant relationship between long distance driving and LBP. Table 37. Relationship of Vibration Exposure and LBP
Vibration Exposure Low Back Pain No Yes Frequency Percentage Frequency Percentage
No 57 43.2 75 56.8 Yes 87 36.4 159 64.6 Chi square = 1.91 P value = 0.16738501 There is no significant relationship between vibration exposure and LBP. Table 38. Relationship of Employee Satisfaction with Management and LBP
Employee Satisfaction with Management
Low Back Pain
No Yes Frequency Percentage Frequency Percentage
I am happy 43 42.2 59 57.8 I am satisfied 76 40.9 110 59.1
I am not satisfied 16 31.4 35 68.6 I am not happy 9 23.1 30 12.8
Chi square = 6.02 P value = 0.11045317 There is no significant relationship between employee satisfaction with management and LBP. Table 39. Relationship of Height and LBP
Height Low Back Pain No Yes Frequency Percentage Frequency Percentage
< 159 7 25.9 20 74.1 160 6 33.3 12 66.7 161 8 50.0 8 50.0 162 7 43.8 9 56.3 163 9 32.1 19 67.9
48
164 3 20 12 80 165 7 30.4 16 69.6 166 7 46.7 8 53.3 167 13 46.4 15 53.6 168 8 23.5 26 76.5 169 5 29.4 12 70.6 170 14 53.8 12 46.2 171 11 52.4 10 47.6 172 5 41.7 7 58.3 173 10 43.5 13 56.5 174 1 9.1 10 90.9
> 175 23 47.9 25 52.1 Chi square = 21.80 P value = 0.14962400 There is no significant relationship between height and LBP. B. Discussion
Factors such as employee satisfaction with management, height, rough
roads, vibration exposure and rough road complaints were found not to be
significantly associated with LBP in the bivariate analysis. However, the p values of
these variables were within 0.06 – 0.20. Review of related literature showed strong
correlation of these variables with low back pain. Thus, they were included in the
multivariate analysis.
1. Insufficient Work Space
Results show that insufficient room space is associated with low back pain.
This is consistent with a study evaluating the seating of Qantas flight deck
crew which showed that postural discomfort due to insufficient room space and low
back pain during flying among middle- and long-distance Qantas pilots were
widespread (33).
An unsuitable workspace that prevents employees from sitting in a balanced
position can cause poor body position. The physical arrangement of workspace
elements such as work surfaces, tools and equipment may not correspond with the
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reaches and clearances of seated employees. The workstation may also be
unsuitable because the seats are too high or low for an employee's body size and
shape. These changes may ultimately lead to low back pain (34).
2. Abnormal Vibration (Whole Body Vibration)
A significant association was also observed between abnormal vibration and
low back pain.
Although reports of low back pain were found to be age-related, there was
evidence that low back pain occurs earlier than expected for workers exposed to
whole body vibration (WBV). WBV is also related to poor working posture,
prolonged sitting posture and inadequate working conditions and contribute to the
occurrence of low back pain (48).
In a related study, a significant relationship was also found between exposure
to hand-transmitted vibration and sensory symptoms. There was no marked excess
of low back pain complaints in workers exposed to WBV, with only moderate
excesses in men exposed above the British Standard and male riders of heavy
industrial vehicles (47).
3. Uncomfortable Sitting Posture
Uncomfortable sitting posture was also observed to be associated with low
back pain.
The type of sitting posture also plays a role in reducing excessive stresses on
the spine, which may lead to LBP (18). Sitting with the back slouched for as little as
20 minutes can result in increased laxity of the posterior spinal ligaments (22).
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4. Constrained Posture
Results show that there is a significant relationship between LBP and
constrained posture.
Posture is the relative arrangement of body parts for a specific activity (1).
Thus, it is important to know and maintain proper posture to avoid stresses which
may cause pain and discomfort. Poor working posture or constrained posture
requires muscles to work at a level near or at their maximum capacity (31). As a
result, there is de-conditioning of the muscles and the entire back becomes sore and
tired, causing low back pain (28).
5. Rough Roads
Rough roads, i.e. rough roads driven and rough road complaints, were found
to be not significantly associated with low back pain.
This is not consistent with the fact that rough roads may result in whole-body
vibration, which occurs while riding vehicles over rough terrain. A related study also
observed a strong correlation between whole body vibration and motor vehicle
driving (44). This may be due to the fact that the bus drivers gave only an estimate
of rough roads experienced while driving.
6. Boredom
Results show that a significant relationship exists between boredom and low
back pain.
Psychological factors are even more important in people with low back pain.
Dissatisfaction with a work situation, a supervisor, or a dead end job and boredom
contribute greatly to the onset and persistence of low back pain (56). Other factors
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which increase the risk of low back pain together with boredom include degree of
focus on the pain, beliefs about the meaning of the pain and a sense of poor control
over the pain (55). In this study, about 66% of the bus drivers who experience
boredom at work have low back pain.
7. Depression
There is a significant relationship between depression and low back pain.
Recent research indicates that in many people, preexisting depression and
the inability to cope may be more likely to predict the onset of pain than physical
abnormalities. People who are depressed are more likely to have vague physical
symptoms, including low back pain. Depression, low activity or high pain behavior,
negative beliefs or fear of pain are the three psychological-behavioral factors that
have continued to show consistent, empirically supported predictive capabilities.
However, it has not been determined which of these factors are greatly involved in
predicting disabling low back pain (53).
8. Frequent Movement of Back
A significant relationship was observed between frequent movement of back
and low back pain.
About 64% of the subjects with low back pain move their backs frequently.
The exact cause of low back pain may be hard to find. Pain can come from muscles,
ligaments, nerves, discs, or bones. People who are inactive are especially at risk of
LBP, are not conditioned, and prone to strains when they move their back frequently.
Repetitive motion injury (RMI), also known as repetitive stress injuries, is a type of
stress injury that results from repetitive motions such as frequent bending or
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sustained awkward positioning performed over extended periods of time without
allowing for sufficient rest (31).
9. Frequent Movement of Shoulders
Results show that frequent movement of shoulders is significantly associated
with low back pain.
Repetitive manipulation of body parts particularly the shoulders while driving
may result in injury or illness of its soft tissues, thus contributing to the development
of low back pain (31).
10. Long Driving Time
Results show that long driving time was significantly associated with low back
pain.
This finding is consistent with a study which showed that driving for eight
hours or more may not protect drivers from harmful vibration exposure leading to low
back pain (51). A related publication also showed that drivers have an elevated risk
for injury that can be attributed solely to their physical working conditions, particularly
the number of hours on the job (42).
11. Long Distance Driving
Results show that long distance driving is significantly associated with low
back pain.
A little over 40% of the subjects drove at a range of 400 to 499 km every day.
Findings from a related study showed that people who drove long distances were at
significantly increased risk of having neck and low back pain. A recent Swedish
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study found significantly increased risks of low back pain among those who drove
long distances and spent a long time each day in their car (41).
12. Vibration Exposure
No significant association was observed between vibration exposure and low
back pain.
Vibration exposure included whole-body vibration and at least 20% rough
roads experienced by the drivers while driving.
This finding is contrary to previous studies conducted on the subject matter
(48, 49, 50, 51). There was sufficient evidence that vibration exposure to drivers
could be a health hazard particularly with regard to back problems. The relatively
high vibration exposure levels combined with long exposure duration and prolonged
sitting are likely to contribute to low back pain. From a study on the association of
whole body vibration and low back pain, it was found that the average WBV level
experienced by drivers of heavy transport vehicles exceeded health, fatigue and
comfort limits of the Australian Standard and most exposures were within the
Caution zone for health according to the current International Standard on whole
body vibration (49). A possible explanation to the negative finding in our study is
that vibration was assessed qualitatively.
13. Employee Satisfaction with Management
Results show that employee satisfaction with the company management is
not significantly associated with low back pain.
This finding is contradictory to previous studies which state that employer
policies, attitudes, and actions determine the satisfaction level of employees, which
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in turn, affects health-related conditions. Social and psychological factors play a role
in how severely someone experiences pain and even vague symptoms. People who
are depressed are more likely to have vague physical symptoms, including low back
pain (53). A related article stated that after accounting for physical work load, a
stressful job with high physiological demands, low satisfaction, and low supervisor
support can cause spinal injury, particularly low back pain (42).
A possible explanation to the negative finding in our study is that information
bias may have occurred. Drivers may not have answered honestly for fear of
dismissal from the company despite assurances of confidentiality.
14. Height
No significant association exists between height and low back pain.
This finding is contrary to previous studies which showed that height is a risk
factor to low back pain. Tall people are at a higher risk of having low back pain than
short people (15). A possible explanation to this finding is that the average Filipino
male height is between 162 and 164 cm (16).
9.3 Multivariate Analysis
The Statistical Package for the Social Sciences (SPSS) version 10 was used
to perform logistic regression. The relationship of risk factors with low back pain was
determined while controlling for the effects of confounders and other independent
variables. The risk factors included age, rough roads experienced, percent of rough
roads, abnormal vibration, vibration exposure, uncomfortable sitting posture,
constrained posture, boredom, depression, frequent movement of back, frequent
55
movement of shoulders, long distance driving, long driving time, height, employee
satisfaction with management and insufficient work space. The confidence level
used was 95% with an α equal to 0.05.
Using the backward Wald method, the independent variables were analyzed.
The study claims that the independent variables from the bivariate analysis would
increase the probability that a driver will develop low back pain. A step-by-step
elimination using the backward-Wald method is shown in Appendix A (Table 42-A
and 42-B).
A. Results
Results showed that three independent variables significantly contribute to
the probability of LBP occurrence among bus drivers. These are constrained
posture, employee satisfaction with management and long distance driving.
Table 40. Risk Factors to Low Back Pain
Variable Odds Ratio and Confidence Interval Constrained Posture 3.013 (1.961,4.880)
Long Distance Driving 2.185 (1.111, 4.299) Employee Satisfaction to Management 1.989 (1.153,3.429)
B. Discussion
1. Constrained Posture
Drivers who experience constrained posture while driving have 3 times
greater risk of having low back pain compared to those who do not.
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De-conditioning, which is the weakening of the muscles supporting the
spine and trunk, occurs due to poor working posture or constrained posture. The
former can cause the entire back to become sore and tired, leading to low back
pain.
2. Long Distance Driving
Drivers who drove for at least 300 km per day have 2.1 times higher risk of
developing low back pain than those who drive for less than 300 km in a day.
According to a study, increased risk of having neck and low back pain was
found among those who drive long distances.
3. Employee Satisfaction with Management
Drivers who experienced dissatisfaction with the management are 2.1
times more at risk of having low back pain than those who are satisfied.
Vague symptoms, including low back pain, are more likely to occur among
depressed individuals. A related article stated that after accounting for physical
workload, a stressful job with high physiological demands, low satisfaction, and
low supervisor support can cause spinal injury, which may lead to low back pain.
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10.0 Conclusion
1. Constrained posture is significantly associated with low back pain.
Drivers with constrained posture while driving have 3 times greater odds of
having low back pain.
This finding suggests that maintaining proper posture will reduce the risk of
low back pain.
2. Long distance driving is significantly associated with low back pain.
Drivers who drive for at least 300 km per day have 2.2 times higher risk of
developing low back pain.
This finding suggests that management should look into the possibility of
modifying work shifts of bus drivers based on a 300 km-maximum distance per
day. Hence, this should not generally affect income of drivers on one hand and
company productivity on the other hand.
3. Employee satisfaction with management is significantly associated with low
back pain.
Drivers who show dissatisfaction to management are 2.1 at risk of having low
back pain.
This finding emphasizes the importance of good management-worker
relationship in improving the drivers’ well being. Thus, better work performance,
less absenteeism and increased productivity will be achieved.
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11.0 Recommendations
1. Health education should be conducted in order to inform the drivers about the
effects of long driving time and low back pain.
The causes of low back pain will be discussed. Posters, fliers and multi-
media showing the latest concepts and preventive measures on low back pain
should be provided. Measures to alleviate and prevent LBP can then be made.
2. Regular medical check-ups should be provided by the company to identify and
address health problems of bus drivers, particularly low back pain.
Low back pain which lasts for less than 6 months is acute. However, it is
considered chronic if it occurs for more than 6 months. Early detection of low
back pain in its acute stage is crucial in the prevention of its progression to
chronicity. Therapy for identified low back pain cases is helpful in improving
worker performance.
At present, no health professionals in companies with 300 or more employees
were observed. As a possible solution, bus companies proximate to each other
may employ a part-time health professional which will provide service to the
cluster of bus companies.
3. The company should provide health fitness training for their employees.
Exercise is important in preventing repeat episodes of low back pain
and avoiding it in the first place. The bus company is recommended to have a
resident physical therapist when teaching its employees on how to exercise
safely. A complete exercise program should include aerobic activity as well as
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stretching and strength training. Aerobic exercise has been reported to improve
or prevent low back pain.
Exercises such as abdominal bracing, neutral spine and basic and
advanced curl ups, side bridge and bird dog exercise are recommended by Joy
M. Beatty, MSPT in order to prevent occurrence of low back pain. (See
Appendix B for detailed exercise descriptions.)
4. The companies should have regular maintenance of their buses.
Previous studies have found that bus engines and seats kept in good
condition reduce whole body vibration exposure due to rough roads and poorly
maintained engines. Also, adjustable seats should be maintained in order to
assure sufficient workspace and comfortable sitting posture of the bus driver.
5. Regular meetings should be conducted by the management in order to assess
the working condition of their employees and immediately address problems.
It has been proven that dissatisfaction with a work condition, a
supervisor and boredom can greatly contribute to the onset and persistence of
low back pain. It is therefore important to address these problems in order to
assure worker satisfaction to management.
6. Drivers with special needs, e.g. older employees, those with serious health
complaints and those recovering from an illness should be given some degree of
flexibility in their work schedule. However, individual adjustments in schedule
should not affect the performance of the whole workforce. Recent research
shows that in many people, pre-existing depression and inability to cope may be
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more likely to predict the onset of pain than physical abnormalities. As a result,
there is a significantly higher absentee rate in spite of less stress in their backs.
7. Bus companies should include health programs to be carried out by medical
professionals such as stress management, lecture/demonstration on proper
driving posture and stretching exercises.
8. Bus companies should consider developing a working schedule that would allow
driving shifts every 300 km. This would minimize the risk of having low back
pain. If driving is extended, drivers should be given enough rest periods of at
least 30 minutes.
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13.0 Acknowledgements We would like to express our deepest gratitude and appreciation to the following individuals without whose contribution we could not have completed this research: Dr. Benjamin C. Vitasa, our beloved adviser, for the “lessons learned” which have taught us to go deep into the heart of our research and for bringing out the best in each of us. Dr. Ethel M. Estanislao, our statistics adviser, whose knowledge has enlightened our path towards the fulfillment of our research. Prof. Jingky Lozano, for so graciously sharing her precious time and giving us advice when we needed it most. Prof. Rosebelle Azcuna, for lifting up our spirits with her insights during moments of confusion. Rowena Yra, Shelly La Rosa and Ricky Hipolito, the fun-loving and ever-dependable research assistants, who have supported us through thick and thin. The management of the bus companies for their cooperation in the conduct of our study: Mr. Jun Belen, station master, Tritran Bus Co. Mr. Ruben Locegro, dispatcher, BBL Trans System Mr. Armando Mendoza, station master, Victory Liner Mr. Ricardo Mercado, Jr., traffic operation staff, Grand Star Bus Co. Ms. Jennifer Bañaga, vice president, administration, Philtranco Ms. Pepita Iraya, inspector, JAC Liner, Inc. Ms. Lucita Limosnero, special trip coordinator, Green Star Bus Co. Ms. Josephine Solomon, head, personnel dept, Pangasinan Five Star The three hundred seventy eight bus drivers who participated in this study, for their time and cooperation. Classmates and friends, especially Emmanuel Paragas, Jr., Joseph Eufemio Martinez and Dennis Pascual for their help and encouragement which has taught us to move on. Mrs. Felicidad Serafico and Jollibee for providing food which gave strength to both our minds and bodies. The CPH guards for giving us help and protection whenever we need one. The song “Maybe” for serving as our inspiration and relaxation in the middle of difficulties. Our parents who has shown much love through their unfailing support and understanding: Mr. Teodoro P. Culla and Mrs. Lourdes M. Culla Mr. Edmar O. Martinez and Mrs. Maura S. Martinez Mr. Joselito S. Santiago and Mrs. Precy R. Santiago Mr. Leroy J. Tad-y and Mrs. Josie M. Tad-y And above all, God Almighty, our light and our protection amidst the challenges of life.
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