PHYSIOLOGY OF AGING
“We are all
amateurs; we don’t live long enough to become anything else.”
Charlie
Chaplin
Significance
of Human Aging
l People live longer now than ever
before
l By 2030, 20% of the US population
will be 65 and older
l Significant challenge to medicine -
ethical, financial, etc.
l What is “normal” in the aging process
- primary aging
l More susceptibility to disease -
secondary aging
l More heterogeneity in the elderly
population
l Onset indeterminable and progression
varied
l Genetic and environmental factors
Gender is a
significant factor
l Lifestyle a primary factor
l Various theories of aging attempt to
explain the process - bottom line, there is disruption of homeostasis
STAGES OF LIFE
l Adulthood is attainment of
physiologically optimal integrated function
l Function in adulthood is the standard
measure
l Unsound and incorrect to state that
changes with aging are necessarily “abnormal”
l Three observations of the elderly:
–
Greater
heterogeneity in responses
–
Changes
in function do not occur simultaneously
–
Changes
in function do not occur to the same degree
l Old age should not be viewed as a
“disease” nor should a time clock be put on aging
Human
Longevity
l Significant increase in longevity
over past centuries
l Due to decline in deaths resulting
from infectious disease along with improved public health
l Heart disease, cancer and stroke now
most common cause of death
l Death rates have actually declined in
the elderly
l Is there a limit to human life span
and should we prolong life at the expense of overall health?
l We should be talking in the context
of “health span” not life span
Successful
Aging
l Chronologic age and physiologic age
not the same
l Due to complex interactions of
genetics and environment
l Individuals “age” at different rates
and there is significant variability
l Prevalence of disease increases with
age
l Proposed pathways of aging:
l Aging with disease and disability
l Usual aging; absence of pathology but
presence of decline in function
l Healthy aging; no pathology or
functional loss
l Pathway goals:
l De-emphasize aging characterized by
decline
l Emphasize heterogeneity among elderly
l Underscore positive pathway of aging
l Highlights possible avoidance of
disease associated with aging
l Heterogeneity of various values and
functions
l Many associated with physical inactivity
l Recent research:
–
Elderly
individuals with weak muscles are at greater risk for mortality than
age-matched individuals
–
Increase
in amount and rate of loss of muscle increases risk of premature death
–
Physical
inactivity is 3rd leading cause of death in US and plays role in chronic
illnesses of DISEASES
Aging and Disease
Aging is associated with increase in
incidence and severity of disease Factors predispose individuals to functional
losses later in life
l Cell senescence much like apoptosis
–
Occurs
throughout life
–
Arresting
growth of damaged/dysfunctional cells
–
Beneficial
early in life; may contribute to aging later
–
Inducers
can cause cancer
–
Senescence
allows cells to respond to inducers, but cells withdraw from growth cycle -
incapable of tumorigenesis
–
Contribution
of cell senescence to aging:
–
Altered
secretions of cells
–
Proteases,
inflammatory cytokines, growth factors
–
Erosion
of structure and integrity of tissues
Current Areas of Research
l Caloric Restriction
l Altered dietary intake
l Insulin-like growth factor (IGF)
l Pharmaceuticals
l Most, if not all, of these have a
similar goal of targeting reactive oxygen species, underscoring what appears to
be a substantial role of oxidants in the aging process
