Physiologyof the

Aging Process

Painting by Domenico Ghirlandaio (Florence 1449-1494)

Spring 2007

Why study aging?Why study aging?1. Increased length of lifespan & increased number of

the elderly in the human population, worldwide

2. Increased proportion of persons aged 65+ in some populations as compared to those aged 14-19

3. This greater human longevity is acknowledged by developing technologies, markets and professions

4. Need to better educate the population in healthy habits

5. Need to support research in biomedicine

6. Points 4 and 5 must take into consideration the entire life cycle as our health today depends on our health yesterday and will influence our health tomorrow

1. Increased length of lifespan & increased number of the elderly in the human population, worldwide

2. Increased proportion of persons aged 65+ in some populations as compared to those aged 14-19

3. This greater human longevity is acknowledged by developing technologies, markets and professions

4. Need to better educate the population in healthy habits

5. Need to support research in biomedicine

6. Points 4 and 5 must take into consideration the entire life cycle as our health today depends on our health yesterday and will influence our health tomorrow

Age

0

20

40

60

80

100

0 10 20 30 40 50 60 70 80 90 100

1900

Per

cen

t S

urvi

ving

1950

2002

Source: Arias E. United States Life Tables, 2002. National Vital Statistics Reports; vol. 53, no. 6.

 Hyattsville, MD: National Center for Health Statistics, 2004. 

Survival Curves for U.S. Population, 1900 to 2002

Probability of 50 year old living to 90, 1900 to 2002

Probability of 50 year old living to 90, 1900 to 2002

2.7

5.0

15.2

3.8

9.6

26.6

0

5

10

15

20

25

1900 1950 2002

Percent Men

Women

30

Source: Computed from U.S. life tables in: Arias E. United States life tables, 2002. National vital statistics reports; vol. 53, no. 6. Hyattsville, MD: National Center for health Statistics, 2004.

Life expectancy and infant mortality throughout human history

Life expectancy Infant mortality rate at birth (years) (per 1000 live births)

Prehistoric 20-35 200-300

Sweden, 1750s 37 210

India, 1880s 25 230

U. S., 1900 48 133

France, 1950 66 52

Japan, 1996 80 4

According to the renowned economist,R.W. FogelFogel

“Health care is the growth industry of the 21st century. It will promote economic growth through its demand for high-tech products, skilled personnel, and new technologies”

According to the renowned economist,R.W. FogelFogel

“Health care is the growth industry of the 21st century. It will promote economic growth through its demand for high-tech products, skilled personnel, and new technologies”

Stages of the Lifespan

Prenatal Life

Ovum: Fertilization - end 1st weekEmbryo: 2nd-8th

weekFetus: 3rd-10 lunar

month

Neonatal Period

Newborn: end of 2nd week

Infancy: 3rd week-1st year

Childhood: 2-15 years

Adolescence: 6 yrs after puberty

Postnatal Life Adulthood

Prime & transition (20-65 yrs)

Old age & senescence (65

yrs+)

Chapter 1, Table 1.1

The journey of life is NOT a simple juxtaposition of successive functional timetables

Rather, physiologic competence at each stage of life:

• is influenced by the functional events in preceding stages

and• influences the degree of competence of the stages that follow The genome dictates the

genetic characteristic of the species

but Genetic expression of each individual within the species may be modified throughout life by the environment

Genome meet your environment!

Thus, longevity depends:not only on genetic inheritance

but alsoon gene-environment interactions

Longevity is an important decision nature must make

Usually important decisions in nature are regulated in a complex way

As organisms become more complex so does the need to balance life and death

The genome proposes

and

the phenome disposes

Increase in longevity over centuries may be related to progress in human civilization as exemplified by

progress in physio-technology

Increase in longevity over centuries may be related to progress in human civilization as exemplified by

progress in physio-technology

•Caused by improvements in agriculture, economics, public health, hygiene, etc.

•Resulting in more efficient functional competence:less infant mortality

better growth delayed occurrence of aging- related diseases

• Manipulation of the environment may prolong the lifespan:

better nutritionmore learning

more physical exercise, etc

For the vocabulary of common

terms related to aging,

see Table 1-2

(Handout)

Methods to Study Physiology of Aging

1. Study in humans a. Cross-sectional methods

• Compare characteristics among different individuals of the same age at one time.

• Rapidity but relative accuracy

b. Longitudinal studies• Examine the same individuals at

regular time intervals throughout life (or portion of life).

• Each person is his/her own control.• Accuracy but difficulty of

repeatedly reaching the same people.

c. Activities of Daily Living (ADL) / Instrumental Activities of Daily

Living (IADL)a. Clinical Studies

2. Study in animals (eg. vertebrates, invertebrates, yeast)• Comparison of physiological

characteristics and longevity among animals.

• Creation of transgenic mice for expression or deletion (knock-out) of specific traits

Methods to Study Physiology of Aging (cont.)

3. In vitro studies (eg. cultured cells, tissues, organs)

Methods to Study Physiology of Aging (cont.)

Microglia (immune cells)

Neuroglia: Astrocytes

Neuroglia: Oligodendrocytes