The Aging Process
Andrew E. Scharlach
University of California at Berkeley
School of Social Welfare
Berkeley, CA 94720
Made possible with partial funding by
The Academic Geriatric Resrouce Program
University of California, Berkeley
Also developed as part of this project are curriculum modules summarizing
information regarding a number of other aging-related topics, including the
following: (1) Demographic characteristics of an aging society; (2) Myths and
stereotypes about aging; (3) Women and aging; (4) Ethnicity and aging. These
curriculum modules are available from the Center on Aging, University of California, 535 University Hall #7360, Berkeley, CA 94720-7360, or from Professor
Scharlach at the School of Social Welfare.
Development of these curriculum materials was made possible by grants from
the Office of Educational Development, the Media Resource Center, the Academic Geriatric Education Program, the American Cultures Program, and the Eugene and Rose Kleiner Chair for the Study of Aging Processes, Practices and Policies.
Andrew Scharlach, Professor of Social Welfare and holder of the Kleiner Chair
in Aging at the University of California at Berkeley, coordinated the overall
project and was the primary author of the sections on cognitive and
personality changes associated with aging. Barrie Robinson, Field Work
Consultant and Lecturer in the School of Social Welfare at the University of California at Berkeley, was the primary author of the sections on the physiology
of aging and sensory changes with aging.
The authors would like to express their appreciation to Paola Timiras,
Professor of Physiology at the University of California at Berkeley, for her
consultation regarding this curriculum module. The authors also would like to
thank Kris Duermeier for her assistance in assembling the annotated
bibliography and list of audiovisual resources. We also are indebted to the
numerous faculty members in Social Welfare and other departments who took the
time to review earlier drafts and make suggestions designed to increase the
usefulness of these materials.
The Aging Process
The curriculum module on the Aging Process consists of six sections: (1)
Physiology of Aging; (2) Sensory Changes with Aging; (3) Cognitive Changes
Associated with Aging; (4) Personality Changes Associated with Aging; (5) an
Annotated Bibliography of suggested readings; and, (6) a list of available
Audiovisual Resources. Instructors are encouraged to adapt these materials as
appropriate to their particular needs. Some instructors may wish to utilize
the content as a source of lecture material; others may wish to assign
sections for student reading and discussion. These materials also may be
useful as background reading for students and professors new to this topic.
However, they are used, it is hoped that these materials will stimulate
increased interest in and knowledge about the aging process as it affects all
of us. For further information regarding how these materials can best be
utilized, instructors are welcome to contact Professor Andrew Scharlach at
the School of Social Welfare, University of California at Berkeley.
Table of Contents
I. Physiology of Aging
· The outward signs of aging
· Changes in the cardiovascular system
· Changes in the respiratory system
· Changes in musculature
· Changes in the skeletal system
· Changes in the nervous system
· Changes in the gastrointestinal system
· Changes in the endocrine system
· Changes in sexuality
II. Sensory Changes with Aging
· Changes in vision
· Changes in hearing
· Changes in taste and smell
· Changes in skin sensitivity
III. Cognitive Changes Associated with Aging
· Learning and memory
IV. Personality Changes Associated with Aging
· Personality stability
· Personality change
V. Annotated Bibliography
VI. Audiovisual Resources
Physiology of Aging
As we age, we undergo a number of physiological changes which affect not only
how we look, but how we function and respond to daily living. Overall, the
changes in the later life span described below involve a general slowing down
of all organ systems due to a gradual decline in cellular activity. It should
be noted that individuals experience these changes differently - for some,
the level of decline may be rapid and dramatic; for others, the changes are
much less significant. The effects of these changes also differs widely.
While approximately 85% of older adults experience chronic conditions, only
about 20% experience significant impairment in their ability to function.
The Outward Signs of Aging
The most common external signs of aging involve the skin, hair, and nails.
Over time, the skin loses underlying fat layers and oil glands, causing
wrinkles and reduced elasticity. Other contributing factors are nutrition,
exposure to the sun, heredity, and hormones. With these changes comes an
increased susceptibility to cold (hypothermia), bruising, and bedsores. There
is also a reduction in the ability to perspire due to atrophy of sweat
glands, making the individual more susceptible to heat (hyperthermia). In
addition, the skin develops "age spots" due to deposits of melanin
pigment. The hair gradually loses its pigmentation and turns gray. The nails
become thicker due to reduced blood flow to the connective tissues.
Changes in the Cardio-Vascular System
The most significant overall change is reduced blood flow to the body, which
typically becomes significant in the eighth decade. This results from a
number of factors including normal atrophy of the heart muscle, especially in
the left ventricle which pumps oxygenated blood out; calcification of the
heart valves; loss of elasticity in artery walls (arteriosclerosis or
"hardening of the arteries"); intra-artery deposits
(atherosclerosis). The reduced blood flow results in reduced stamina since
is being exchanged, reduced kidney and liver function, and less cellular
nourishment. As a consequence, the individual is more susceptible to drug
toxicity, has a slower rate of healing, and a reduced response to stress.
Other consequences of these cardio-vascular changes are hypertension with an
increased risk of stroke, heart attack, and congestive heart failure.
Changes in the Respiratory System
As with the cardio-vascular system, there is also a reduction in the
efficiency of the respiratory system in later life. The airways and lung
tissue become less elastic with reduced cilia activity, resulting in
decreased oxygen uptake and exchange. The muscles of the rib cage also
atrophy, further reducing the ability to breathe deeply, cough, and expel
carbon dioxide. These changes are exacerbated if the individual smokes or
lives in a polluted environment. The consequences of these changes can
include decreased stamina with shortness of breath and fatigue, which in turn
may impair one's ability to perform activities of daily living. Lack of
oxygen can also increase anxiety.
Changes in Musculature
A generalized atrophying of all muscles is normal in later years accompanied
by a replacement of some muscle tissue by fat deposits. This results in some
loss of muscle tone and strength. Some specific implications are reduced
ability to breathe deeply; reduced gastro-intestinal activity which can lead
to constipation; and bladder incontinence, particularly in women. Although
everyone experiences these changes to some degree, regular physical exercise
appears to temper the extent of these changes.
Changes in the Skeletal System
Beginning at around age 35 in both men and women, calcium is lost and bones
become less dense. This can result in osteoporosis and a reduction of weight
bearing capacity, leading to the possibility of spontaneous fracture.
Thinning of the vertebrae also results in a reduction in height. In addition,
the vertebrae calcify, resulting in postural changes and increasing rigidity,
making bending difficult. The joints also undergo changes. In fact,
arthritis, the degenerative inflammation of the joints, is the most common
chronic condition in the elderly. The two most common forms are
osteoarthritis, a wearing away of the joint cartilage, and rheumatoid
arthritis, a disease of the connective tissue. These conditions can impair
mobility and the performance of daily activities of living.
Changes in the Nervous System
After age 25, everyone loses nerve cells. Gradually over time, this results
in a reduced efficiency of nerve transmission, affecting response time and
coordination. The brain also shrinks in size, which does not significantly
affect functioning except in the most extreme cases. These changes may also
affect sleeping patterns somewhat by decreasing the length of total sleep
time and REM sleep.
Changes in the Gastrointestinal System
As we age, we experience a reduction in the production of hydrochloric acid,
digestive enzymes, and saliva, as well as a reduction in the total number of
taste buds. These changes can result in gastrointestinal distress, impaired
swallowing, and delayed emptying of the stomach. Perhaps more importantly,
the breakdown and absorption of foods may also be impaired, sometimes
resulting in vitamin deficiencies of B, C, and K vitamins or, in extreme
cases, malnutrition. If left untreated, these deficiencies may result in
capillary weakening, easy bruising, muscle cramping, reduced appetite,
weakness, mental confusion and/or illness.
Changes in the Endocrine System
The endocrine or metabolic system is responsible for changing food into
energy. After age 25, everyone experiences approximately a 1% decrease per
year in their metabolic rate. This overall slowing results in food being less
well absorbed and utilized as well as a decrease in the overall metabolism of
drugs. Consequences can include reduced stamina and reserves as well as
greater susceptibility to drug toxicity.
Changes in Sexuality
Overall, sexual activity is more related to past life patterns than to age.
Sexual desire and performance may continue well into an individual's seventh,
eighth and ninth decade although frequency may diminish. Physiological
changes in women include atrophy of the ovarian, vaginal, and uterine tissues
with decreased production of vaginal fluids. In men, sperm production is
decreased, the prostate enlarges, and overall sensitivity declines. Both
older men and women generally require more stimulation to become aroused and
more time to reach orgasm.
Sensory Changes with Aging
Our senses play a central role in our ability to gather information and to
participate in social interactions. Along with a variety of physiological
changes which accompany the aging process, changes in the sensorium also
occur. It should be noted that while everyone will probably experience some
of the changes discussed below, the degree of change will vary from person to
person. In addition, the effects of the sensory changes on the individual's
perceptions and social interaction depend upon many factors, such as the specific
sense affected, the nature of the change, and the extent to which remediation
for the changes can be accomplished.
Changes in Vision
Beginning the fourth decade, the pupil begins to decrease in size and in
response time to light. Because of these changes, it is estimated that older
adults require three times the amount of illumination to see as a younger
person. Also, focusing takes longer with an increase in nearsightedness,
making small print harder to read. Another normal change is thickening and yellowing
of the lens of the eye. This results in light diffraction, increased
sensitivity to glare, decreased depth perception, and more difficulty
distinguishing pastel colors, especially blues and greens.
Non-normal changes of the eye include cataracts or significant opacification
of the lens, glaucoma, and various retinal disorders such as macular
degeneration and diabetic retinopathy.
Changes in Hearing
Hearing changes that are common as we age include a decrease in sensitivity
to high frequency tones and decreased discrimination of similar pitches.
These changes are usually the result of normal changes to the bones and
cochlear hair cells of the inner ear.
Significant hearing loss, while relatively common in the elderly population,
is not a normal part of the aging process. Approximately 30% of all elderly
persons have some hearing impairment. Such loss is usually the result of
damage to the hearing organ, the peripheral nervous system, and/or the
central nervous system. Depending upon the specific cause and location of the
problem, different types of hearing loss may result, such as high tone loss,
flat hearing loss, and difficulty understanding or distinguishing words.
Because most hearing changes are not amenable to medical or surgical
intervention, hearing aids and aural rehabilitation are usually indicated,
although not all types of hearing loss are remediable. Because hearing is
essential for social interaction and safety, untreated hearing loss is
perhaps the most socially disabling of all sensory impairments. It is an
invisible disability which is often covered up or denied by a person who may
then be mislabeled as senile, dumb, or uncooperative.
Changes in Taste and Smell
Taste and smell are interrelated and important for eating as well as checking
for hazards in the environment such as spoiled food, smoke, and fumes. Older
adults experience some decline in the ability to taste resulting from a
reduction in the total number of taste buds, especially after age 80. Some
individuals also experience a decline in their sense of smell, but this is
usually from non-normal conditions such as blockage or disease of the
olfactory receptors in the upper sinus. Some consequences of these changes
include a decreased interest in food, a desire for more salty or highly
seasoned food, and a reduced awareness of body odor and environmental hazards
such as spoiled food, smoke, and hazardous fumes.
Changes in Skin Sensitivity
With advanced age, the skin becomes somewhat less sensitive to sensation,
including heat, cold, and injury. While this is relatively inconsequential
for most people, it can pose a serious threat for those whose insensitivity
is extreme. Perhaps more important, however, is the recognition that touch is
one of our most important senses all through life. It serves many important
functions such as forming a sense of self, relieving stress, giving comfort,
maintaining intimacy, and conveying acceptance and connectedness. Because
older adults typically have less opportunity to give and receive touch, they
may lose the benefits that these functions impart.
Cognitive Changes Associated with Aging
Research on the human brain has documented dramatic decreases in brain size
and efficiency throughout our lives, beginning virtually from the time of
birth. Yet, in spite of these anatomical and physiological declines, studies
have found evidence of only limited decrements in actual intellectual
functioning associated with the aging process. This section examines some of
these known decrements in two fundamental domains of cognitive functioning:
(1) intelligence, and (2) learning and memory.
The fact that most older persons experience virtually no functional
impairment despite their cognitive limitations is a testimony to the
redundancy built into the human brain, as well as the ability of humans to
find ways to compensate for potential cognitive limitations. It also reflects
the fact that intellectual ability is only one of many factors affecting
functioning in later life. Ultimately, intellect may be considerably less
important than are self-care ability and social competence in determining an
older person's ability to function independently and competently, and to live
a rich, rewarding life.
Intelligence generally can be thought of as including a range of abilities
that allow us to make
sense of our experiences: the ability to comprehend new information, the
ability to think abstractly, the ability to make rational decisions, spatial
ability, numerical ability, verbal fluency, etc. Some abilities (e.g., the
ability to think abstractly) are heavily biologically determined and are
relatively independent of particular applications, reflecting what has been
called "fluid intelligence." Other intellectual abilities (e.g.,
verbal fluency) are more apt to reflect the knowledge and skills a person has
gained through life experience, or "crystallized intelligence."
Intelligence tests have demonstrated a pattern of age-related changes in
intellectual functioning typically beginning after the age of 60. This
"classic aging pattern" involves somewhat poorer performance on
tests of fluid intelligence, but little or no difference on tests of
crystallized intelligence. It should be noted, however, that there is a great
deal of variability in the test scores of older adults, with some older
persons actually doing better than some younger persons. Moreover, older
adults' intellectual functioning can be improved significantly with training
and practice, although improvements generally are less than those experienced
by younger persons with the same amount of training.
The fact that older persons seem to perform more poorly on tests of fluid
intelligence is due in part to reduced efficiency of nerve transmission in
the brain, resulting in slower information processing and greater loss of
information during transmission. However, performance decrements may also be
due to a variety of non-cognitive factors, including impairments in motor
ability and sensation. Slower motor performance can significantly reduce an
older person's ability to respond on tests that require fine hand movements
(e.g., filling in the proper rectangle on an answer sheet). Sensory deficits
associated with aging, for example, can result in perceptual inaccuracies,
requiring the aging mind to commit more attention and cognitive effort to
comprehending sensory input and reducing its capacity to quickly process new
Other factors affecting cognitive performance in older adults are only
indirectly related to the aging process itself. For example, older persons
typically have fewer years of education. They also are likely not to have as
much experience taking intelligence tests as do younger persons who grew up
in an era of widespread intelligence testing, resulting in reduced
familiarity and increased test anxiety for older test takers. Moreover, the
content of these tests often is less meaningful for older persons, reducing
their motivation for committing precious time and energy on difficult test
items that have little personal meaning.
When making decisions, older persons have been found to sacrifice speed for
accuracy, rejecting quick, simplistic solutions to problems and preferring to
work slowly, examining issues from a variety of perspectives before selecting
a response. Finally, many of the health problems which are more common in
later life (e.g., cardiovascular problems) can significantly affect cognitive
functioning as well as test-taking ability.
Not all cognitive changes in later life are negative, however. Older persons
typically exhibit greater experience-based knowledge, increased accuracy,
better judgment, and generally improved ability to handle familiar tasks than
younger persons. Such applied knowledge, or wisdom, may in fact be
considerably more important to one's ability to accomplish most tasks of
day-to-day life than are the abstract abilities tapped by intelligence tests.
Even when physical or cognitive competencies are affected by the aging
process, older adults often are able to develop strategies for compensating
partially or totally. For example, older typists have been found to type as
quickly and as accurately as younger typists even though they are unable to
move their fingers as fast, because they have developed a better ability to
anticipate upcoming words and locate the proper keys on the typewriter. In
general, older adults can perform about as well as younger persons on tasks
which provide sufficient opportunity to compensate for slower physical and
Learning and Memory
Most persons experience a modest increase in memory problems as they get
older, particularly with regard to the ability to remember relatively recent
experiences. Decrements are found both in the
ability to accumulate new information and in the ability to retrieve existing
information from memory storage, although there is little decline in the
ability to store new information once it is learned.
The process of learning new information and encoding it for storage requires
more time as individuals get older, because of the reduced efficiency of
neural transmission and because of sensory deficits that limit one's ability
to quickly and accurately perceive information to be learned (as discussed
above). In fast-moving day-to-day experiences, this may prevent individual
experiences (e.g., the name of someone to whom one is introduced) from
receiving the attention needed for complete encoding into secondary memory.
In addition, the extensive life experience of older persons makes it more
likely that new information will not adequately be distinguishable from
previous learnings (e.g., the names of other similar people one has met over
the years), making it difficult to establish unique cues and linkages for new
Older persons also experience decrements in their ability to retrieve
information once it is stored. In part, this is because of the difficulty
identifying just the right piece of information from the vast store of
information they have accumulated over a lifetime of experiences. This can be
particularly difficult when the new information resembles previously learned
information (e.g., when one is trying to recall a phone number from the
thousands of phone numbers that have been learned over a lifetime).
Consequently, older persons tend to do considerably worse than younger
persons on tests of free recall, where they are asked to retrieve learned
information but given only minimal cues. However, few decrements are found
when older adults are given sufficient orienting parameters to limit the
scope of the search, or are asked to select the correct answer from among a
small number of options (e.g., on a multiple choice test).
Older persons seem to have better memory for certain events that occurred in
the distant past than for recent experiences. To a large extent, this is
because the distant events that are remembered are those which either have
special personal significance (e.g., the birth of a child, the end of World
War II) or are so unique that they are not affected by subsequent experiences
(e.g., childhood occurrences). Such experiences are apt to have been
rehearsed mentally numerous times throughout one's life, increasing their
familiarity and making them easier to recall than are mundane aspects of
one's day-to-day life. In addition, it is considerably more difficult to
validate the accuracy of information from the distant past than it is to
validate more recent information, so that errors in remembering recent events
usually are more obvious than are errors regarding distant events.
Finally, it is important to note that cognitive processes such as learning,
memory, and intellectual functioning are extremely responsive to a person's
physical and psychological state. Physical illnesses and medications can
affect neuronal function and also reduce the energy available for cognitive
processes. Depression and other emotional conditions that involve impaired
self-esteem and reduced confidence in one's own abilities can significantly
impair one's motivation for learning and remembering new information. Among
depressed older adults, for example, memory complaints can increase and
memory performance can decline even in persons who do not have any actual
impairment in cognitive functioning or learning ability. Moreover, older
adults who have adopted the popular stereotype that forgetfulness is
inevitable in old age may experience increased anxiety and reduced
self-confidence when confronted with normal memory tasks, resulting in memory
problems they would not otherwise have had.
Personality Changes Associated with Aging
Personality changes associated with aging have been debated almost since the
beginnings of modern psychology. Freud, for example, believed that
personality development was relatively complete by the time a person reached
adolescence and that little change was possible after the age of 40. Jung, on
the other hand, argued that personality develops throughout one's life in
response to changing life experiences.
Longitudinal studies of personality traits have found that basic personality
traits remain relatively consistent throughout one's adult life. The
Baltimore Longitudinal Studies, for example, found remarkable stability over
periods of ten years or more on personality inventories measuring traits such
as neuroticism, extraversion, and openness to experience. A Minnesota study
obtained similar findings for periods of up to 30 years. Moreover, interviews
with older adults themselves have found that individuals' own self-images
seem to change relatively little as they age, leading some anthropologists to
posit that the self is essentially "ageless."
Whereas basic personality traits may remain rather stable throughout
adulthood, relatively predictable shifts may occur in other aspects of a
person's personality. One of the best documented personality changes in
adulthood is an increased preoccupation with one's inner life, including
greater attention to personal feelings and experiences and reduced
extraversion. This increased interiority often is accompanied by a tendency
to be less impulsive and more circumspect than at earlier ages. In some, it
may be accompanied by greater cautiousness and decreased interest in the
A second domain in which age-related changes have been found concerns gender
role identity. As they age, men and women appear to become more similar in
terms of their values and personality styles. Studies in a number of
different cultures have found that men tend to become more nurturant, expressive,
and affiliation-seeking as they grow older, whereas women tend to become more
instrumental and achievement-oriented. It is not clear whether these shifts
reflect true personality changes or are simply a result of differential role
opportunities across the life cycle (e.g., retirement may provide an
opportunity for men to express nurturant qualities that are not seen as
adaptive at work, whereas the end of child-rearing responsibilities may allow
women an opportunity to express achievement-oriented qualities).
Any attempt to identify predictable personality changes in later life should
note that longitudinal studies have found that adults tend to exhibit greater
inter-individual differences as they grow older. Interaction styles become
more individualized and people may appear to be "more themselves"
than at any other time of their lives. To some extent, this may be a result
of a decreased need to conform to external expectations, particularly in
societies that lack clear and unambiguous social role norms for older adults.
In addition, it is likely that persons of any age may become somewhat less
flexible when faced with the types of social and role losses typically
experienced by older persons. Finally, there is some evidence that persons
with stronger, more inflexible personalities may have lower mortality rates
in certain situations, causing them to be overrepresented among the elderly.
Carlsen, M. B. (1991). Creative aging: A meaning-making perspective. New
York: W. W. Norton & Co.
This book is unique in its blending of the theoretical and the practical.
Attention is given to discussions of perspectives on aging, definitions of
creativity, theoretical frameworks, a set of therapies for aging creatively,
and cognitive habits and cultural tendencies that interrupt creative aging.
Craik, F. I., & Salthouse, T. A. (Eds.). (1992). The handbook of aging
and cognition. Hillsdale, NJ: L. Erlbaum Associates.
Presents reviews of the core topics of cognitive psychology (attention,
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to real-life situations.
Fabris, N., Harman, D., Knook, D. L., & Steinhagen-Thiessen, E. (Eds.).
Physiopathological processes of aging: Towards a multicausal interpretation.
New York: New York Academy of Sciences.
Presents biomedical studies of the aging process, discussing the diversity of
aging phenomena and the mechanisms involved in aging rather than focusing on
a single "main cause" theory of aging. Many different approaches
are included to provide a comprehensive picture of the current state of the
aging field and its future.
Felton, B. J., & Revenson, T. A. (1990). The psychology of health: Issues
in the field with special focus on the older person. In I. Parham, L. Poon,
& I. Siegler (Eds.), ACCESS: Aging curriculum content for education in
the social-behavioral sciences. New York: Springer.
This module presents a current view of the psychology of health and aging. It
describes, in an overview, the state of our current knowledge in the area of
health psychology with a special focus on older people. It includes an
outline of issues to be covered in courses on this subject as well as an
extensive annotated bibliography.
Fiske, M., & Chiriboga, D. A. (1990). Change and continuity in adult
life. San Francisco, CA: Jossey-Bass Inc.
The authors present a wealth of interdisciplinary information in which they
assess stability and change in adult life. They draw on the findings of a
twelve-year study that examines the complex interplay of personality traits,
gender, social factors, and stressors in shaping adult development.
Saxon, S. V., & Etten, M. J. (1994). Physical change and aging: A guide
for the helping professions (third edition). New York: Tiresias Press.
This popular text on normal aging is useful for those in the helping
professions. Neither superficial nor highly technical, it provides up-to-date
and reliable information in straightforward language enhanced by
illustrations. Although the book focuses on the physical changes and common
pathologies associated with aging, it also emphasizes their impact on the
psychosocial behavior of the older person.
Timiras, P. S. (Ed.). (1994). Physiological basis of aging and geriatrics
(second edition). Boca Raton, FL: CRC Press.
This text represents an excellent overview of the aging process from a
physiological viewpoint, examining all systems of the body and describing
changes that occur with normal aging and in disease. Integrated aspects of
aging are considered, and preventive and interventive measures for ensuring
healthful aging are discussed.
Weale, R. A. (1992). The senescence of human vision. Oxford, England: Oxford
As the life expectancy of the human race continues to grow, the subject of
ocular and visual aging is receiving a great deal of experimental attention.
This book reviews existing knowledge re
garding vision and aging, and it provides an excellent introduction to this