institute of energy and sustainable development towards thermal comfort prediction for the older...

Institute of Energy and Sustainable Development

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


Presentation Outline

• Information on Aging

• Aging effect on the body

• IESD-Fiala thermoregulation model

• Insight into the New Model

• Simulation and Results


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.


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]


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]


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.


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]



• 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]


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


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


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.


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


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


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..

institute of energy and sustainable development towards thermal comfort prediction for the older...

Documents

body institute of energy

results institute of

sustainable developmentagingis

chronological age

advancing age

year age group

body functions

heat wave attributable