Introduction to Human Aging

1. longitudinal studies of humans

2. cross-sectional studies of humans

3. lower animal studies

a. known genetic make-up

b. controlled environment

c. short life spans

A. Methods used to study aging

B. Number and percentage of the elderly

1. In the US, more persons > 65 than < 25 years of age

Introduction to Human Aging

2. Median age was ~32 in 1995; was 36 in 2000, and will be ~42 by 2040

year pop. number > 65 % of elderly

1900 75.6 mil 3.1 mil 4.1

1940 132.3 mil 9.0 mil 6.8

1960 181.0 mil 16.6 mil 9.2

1980 228.0 mil 25.6 mil 11.2

1990 250.0 mil 31.2 mil 12.5

2000 268.5 mil 34.9 mil 13.0

2030 304.7 mil 64.6 mil 21.2

C. Percentages of the elderly

Introduction to Human Aging

1. 30% of health care resources used by persons >65 years (will increase to 50% by 2030)

D. Problems for younger members of society

Introduction to Human Aging

2. Older persons require more social services and specialized recreational facilities; these require money (increased taxes)

3. The burden of support falls now and will fall more heavily on the younger generations.

1. Aging is a continuing, normal process.

E. General effects of aging

Introduction to Human Aging

2. Begins at maturity, ends with death

3. Effects of aging increase at age 40

4. Aging is influenced by interactions of genetics and environmental factors.

% at age 60 % at age 80

nerve conduction velocity 96 88

basal metabolic rate 96 84

cardiac index 82 70

kidney function 96 61

renal plasma flow 89 51

vital capacity 80 58

maximal breathing capacity 80 42

F. Estimated declines in some functions with age (age 30 = 100%)

Introduction to Human Aging

1. based on two Greek roots

“homoi” = same

“stasis” = standing still

2. Homeostasis is the sum of all bodily processes, maintaining constancy within limits.

3. In the absence of homeostasis, dysfunction of the organ systems is more likely, and aging increases the likelihood of death.

G. What is homeostasis?

Introduction to Human Aging

H. What is a feedback system?

Introduction to Human Aging

time

function

high

low

steady state

1. Negative feedback

2. Positive feedback

I. Common terms related to aging

Introduction to Human Aging

1. Aging

2. Senescence

3. Senility

4. Elderly vs. old vs. very old

5. Gerontology

6. Geriatrics

7. Longevity (mean vs. maximum)

8. Demography

1. Body structural changes

a. gradual decline in height beginning in the late 30’s

i. shortening of lower limbs due to decreasing joint size and feet arches

ii. shortening of trunk due to increase in normal vertebral column curvature and compression of discs

b. gradual deterioration of muscle, causing shoulder width to decrease

J. General aging changes in the body

Introduction to Human Aging

c. increased fat deposition in abdomen, hips increase in width

d. loss of lung elasticity, leading to increased respiratory effort and increased thoracic circumference

e. changes in body weight

i. men increase weight until mid-50’s, then lose

ii. women gain weight into the 60’s, then lose

1. Body structural changes

J. General aging changes in the body

Introduction to Human Aging

a. total body water

i. young man -- average water = 60% of body weight; drops to 54% with aging

ii. young woman -- average water = 52% of body weight; drops to 46%

b. changes in skin thickness

i. in general there is a gradual but steady decline in skin thickness

ii. extra adipose tissue accumulates around organs rather than in hypodermis

2. Body compositional changes

J. General aging changes in the body

Introduction to Human Aging

i. movement becomes more difficult

ii. breathing becomes more difficult

iii. elevated blood pressure

iv. changes in dietary habits

v. changes in urinary frequency and bowel movementsC

a. Most noticeable changes

3. Body functional changes

J. General aging changes in the body

Introduction to Human Aging

b. Functional changes dependent on genetic make-up, lifestyle history, and environment

end

3. Body functional changes

K. Importance of regular health exams

Introduction to Human Aging

a. Generally accepted standard intervals

b. Baseline info for the MD as patient ages

c. Early detection of problems

d. Examples

i. physicals = >70 annualy; 60-70 biannual; 40-60 triannual; 20-40 every 5 years

ii. blood pressure and Pap smear = yearly

iii. cholesterol = every 5 years

iv. proctosigmoidoscopy = every 3 years at 40; yearly at 50