|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 162
8
Conclusions
The elderly constitute the fastest-growing segment of the pop-
ulation in many industrial countries. This unprecedented demo-
graphic phenomenon is occurring at a time of increasing complex-
ity of environmental factors, including pollutants, pharmaceutical
use, nutrition, and life-style. The impact of these environmental
phenomena on aging processes and the aged is not well under-
stood, but there are sound biologic reasons to assume that the
effect of the environment on people changes with age, as does the
ability to respond to environmental exposures.
In addressing the issues related to aging in today's environ-
ment, one must recognize at least three important questions: What
is the nature of aging? What is the nature of the environmental
exposure? What is the physiologic or medical condition of the
aging or ages] subject or population?
The nature of the aging processes has been a question since
humans have been aware enough of themselves to ask it. Not much
progress has been made toward answering it.
Environmental exposures vary greatly among individuals.
Such exposures might well be more problematic for the aged,
especially those with existing chronic diseases. Over 70~o of the
aged take one pharmaceutical regularly; and heart disease occurs
in over 25~o. These changes in physiologic and medical conditions
162
OCR for page 163
CONCLUSIONS
163
of aging reflect the effects of the environment on intrinsic aging
processes integrated over a person's lifetime.
In addition, it should be understood that the term aged means
different things to different people. More important, aged simply
refers to a portion of the normal distribution of ages In any pop-
ulation defined by any number of objective, functional, or other
· —
criteria.
After extensive review of the current state of the science and
after deliberation of the above questions, the committee drew the
following conclusions.
Evidence supports the concept of intrinsic aging, and many
theories have provided insight into its basic mechanisms. Numer-
ous components of the environment have been shown to cause
changes that simulate and are often confused with features of in-
trinsic aging. For example, habitual sun exposure and cigarette
smoking accelerate aging of the skin, exposure to ultraviolet ra-
diation promotes cataract formation, and exposure to naturally
occurring or industrial or other toxicants can contribute to age-
related neurologic disease. However, no single agent has ever been
shown to cause the earlier appearance of at! aging processes.
Humans exhibit varied responses to the environment and var-
ied patterns of aging. The variation can be attributed to many
factors, which include the following:
.
Differences in individual environment, including nutrition,
pharmaceuticals, lifestyle, and occupation.
. Inborn genetic differences, such as variations in genes that
influence susceptibility to graying of the hair, cataract formation,
diabetes, aging of sun-exposed skin, and metabolism of drugs.
. Interactions between individual genetic constitutions and
the environment.
Information on the specific impact of environmental factors
on aging processes remains scant. However, experimental animal
studies of dietary restriction and genetic manipulations (e.g., set
lective breeding) that extend the life spans of some laboratory
animals are promising tools for the study of aging processes and
the impact of the environment on them.
With regard to the human aged, not enough is known about
the specific effects of environmental exposures, but there is much
evidence of their importance. Consider the following, for example:
OCR for page 164
164
AGING IN TOD~Y'S ENVIRONMENT
~ Extremes of air pollution or environmental temperature
that are tolerated by young adults can be injurious, even fatal, to
the elderly.
. Although the judicious use of medications undoubtedly
contributes to the overall well-being of older persons, they suffer
adverse reactions to drugs more frequently than the young. The
extent to which that is due to dmease severity, use of multiple
drugs, drug misuse, or age itself is unknown.
Older persons are often more susceptible than young adults
to the effects of environmental toxicants.
~ A decrease in smoking, an increase In exercise, control
of hypertension, and dietary modification appear to decrease or
delay the occurrence of heart disease, stroke, and some types of
malignancy.
Interpersonal relationships can have substantial positive
effects on various physical health indexes, and sense of purpose
is closely tied to the health and well-being of the elderly. There
is evidence of greater survivorship among people who have goals
than people who do not, en c} among those who have organize
tion in their daily lives and behavior than those who do not.
Health-care providers, in nursing homes in particular, should be
educated about the benefits to the elderly of increased autonomy
and friendships.
Although the increased incidence of chronic dmeases is often
associated with aging, such diseases need not be characteristic of
the aging processes. The wide variation in the incidences of chronic
diseases in the aged in different countries strongly indicates that
much of the prevalence of these diseases might be preventable.
One appealing and testable hypothesis is that reduction of dmease
in old age is an attainable objective that can be approached, in
part, through modification of the environment. Research in this
field will likely lead to an improved understanding of the interplay
between aging processes, the environment, and disease and help
to provide the key to preventing environmentally induced age-
associated diseases.
Representative terms from entire chapter:
intrinsic aging
