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Towards thermal comfort prediction for the older population: a review of aging
effect on the human body
Divine T. Novieto, Dr. Yi Zhang
21st May 2010
IESD PhD Conference: Energy and Sustainable Development
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Presentation Outline
• Information on Aging
• Aging effect on the body
• IESD-Fiala thermoregulation model
• Insight into the New Model
• Simulation and Results
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Aging
• Is the detrimental changes with time that underlie an increasing vulnerability to challenges thereby decreasing the ability of the organism to survive.
• Also referred to as the progressive accumulation of changes with time that are associated with the ever-increasing susceptibility to disease and death which accompanies advancing age.
• Most developed countries have accepted the chronological age of 65 years as a definition of 'elderly' or Old person.
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Some Theories of Aging
• Wear-and-tear -Normal wear and tear causes cells to function improperly
• Cellular- Cells replicate a specific number of times and then die.
• Nutritional Model Theory- Animals fed 50-60% less than it eats on its own lives longer
Assumption: Lean mass, as opposed to adipose tissue results in greater health
Ref [1]
Ref [2]
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The Aging Situation
0%
5%
10%
15%
20%
25%
30%
2010 2020 2030 2040 2050
65+ 80+
As we age, we experience changes in our solid organs and body functions, these changes lead to diminished physiological reserve resulting in the inability of the body to maintain thermal comfort in times of challenge (hypothermia & hyperthermia)
Aging of populations around the world with nearly 20% gain from age 65. By 2020 one fourth of the population in many nations around the world will be over 601. Fig 1 the Europe situation.
Ref [3]
Ref [4]
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Age Concern
• In the 2003 heat wave, more than 2000 deaths were attributed to the August heat wave in England & Wales. Excess mortality was 33% in those aged 75+ and 13.5% in the under 75 age group during the 10 day heat wave.
• Deaths at home increased by 33% among those aged 75+, and deaths in Nursing homes increased by 42%. Around one quarter of the heat wave attributable deaths occurred in care homes.
• In France excess mortality was estimated at 20% for those aged 45-74 years, at 70% for the 75-94 year age group, and at 120% for people over 94 years.
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Effects of Aging on the Body
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Effects of Aging on the Body
• Skin:-
Loss of subcutaneous fat, thinning of skin, decreased collagen, less sweat glands and difficulty in regulation of temperature.
• Musculoskeletal system:-
Adipose tissue increases and lean body mass decreases, bone mineral content decreases, decrease in height from narrow vertebral spaces and increased arthritis.
Ref [5]
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Effects of Aging on the Body
• Heart:-
Limits of heart exertion reduced with age, Heart less able to pump efficiently, Blood vessels lose elasticity with age making heart have to pump harder to circulate blood
• Central Nervous system:-
Neurons of central and peripheral nervous system degenerate, Nerve transmission slows (slower reflexes), hypothalamus less effective in regulating body temperature.
Ref [6]
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The aging impact diagram
• The inter-relationship between the various components of the body including muscle, heart, central nervous system, skin and the effect aging as a natural phenomenon have on them.
HEART
CENTRAL NEVOUS SYSTEM
VEINS & ARTERIES
SKIN
AGEING EFFECT
REDUCED NEURAL
RESPONSES
ARTERIES & VEINS
STIFFNESS
REDUCED HEART OUTPUT
FRAGILE & LESS ELASTIC
REDUCED VASODILATION REDUCED
SWEATING ABILITY
REDUCED SHIVERING POTENTIAL
REDUCED VASOCONSTRICTION
REDUCED SKIN SENSITIVITY
REDUCED MEAN ARTERIES PRESSURE
REDUCED BLOOD PERFUSION
REDUCED METABOLIC
RATE
SEDIMENTARY LIFESTYLE
MUSCLELOSS OF ACTIVE MUSCLE MASS
CHANGED THERMOREGULATION
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The IESD-Fiala Model
IESD-Fiala model form the basis of this research and profiles the human body as two interacting systems, i.e. the controlled passive system (body structure) and the controlling active system (the thermoregulatory functions). The passive system diagram below is the focus of this paper.
19 spherical and cylindrical elements
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Revised model parameters
ItemTypical person(Fiala model)
Typical old person(75yrs)
Change
BMR (W) 87 70 -19.2%
Cardiac Output (L/min)
4.73 4.05 -14.4%
Body Weight (kg) 73.3 66 -10%
Height (m) 1.72 1.66 -3.5%
Body Surface Area (m2)
1.86 1.73 - 7%
Simulation scenario
Relaxing for 90 min in a pre-test
chamber at 240C dry bulb (Ta)
In test chamber
Temp. 300CIn test chamber Temp. 150C
In test chamber Temp. 300C
90min 60min 120min 60min
240min330min
• A transient simulation was carried out using the original IESD-Fiala model (FM) and the older person model (OP) to compare their dynamic responses to changing thermal environments of:- hot, cold and hot i.e. (30-15-30)0C.
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Results
27
28
29
30
31
32
33
34
35
0 60 120 180 240Time(min)
Skin
Tem
p(0
C)
FM OP
30 15 30
28.5
29
29.5
30
30.5
31
31.5
32
32.5
33
0 60 120 180 240
Time(min)
Skin
Tem
p.(
0C
)
FM OP
30 15 30
Hand (palm) temperature Feet temperature
33.5
34
34.5
35
35.5
36
0 60 120 180 240Time(min)
Skin
Tem
p (
0C
)
FM OP
30 15 30
33.4
33.6
33.8
34
34.2
34.4
34.6
34.8
35
35.2
35.4
35.6
0 60 120 180 240Time(min)
Skin
Tem
p(0
C)
FM OP
30 3015
Lower arm temperature Lower leg temperature
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Conclusion
• The results from the simulations suggest that under the test conditions skin temperatures on the hand (palm), foot, lower arm, and lower leg were lower in the older person than in the average person.
• These findings are in line with earlier studies (Inbar, 2004):-that age related characteristics affect the overall rate of heat gain as well as the mechanisms through which this heat is dissipated.
• And (Anderson, 1996):- peripheral thermosensitivity appears to be progressively attenuated with age
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Finally
• The aim of this research is to develop a customized computer model for predicting thermal comfort of Old persons. The model is expected to predict old persons thermal responses (physical and physiological) and enable designers to estimate their comfort needs and reactions to diverse environmental conditions at the design stage.
• Hopefully we shall move …..from…this….
• To ……..this..