488 Adult Development and Aging
emerging areas in developmental health psychology with par-
ticular attention to problems associated with cancers.
WHAT HEALTH PSYCHOLOGISTS NEED
TO KNOW ABOUT AGING
When we consider the age group 65 to 69, 83% have no dis-
ability and only 3% are in nursing homes; at ages 85 to 89,
45% have no disability and 15% are in nursing homes; by age
100, 18% have no disability and 48% are in nursing homes
(Siegler, Bosworth, & Poon, in press). Thus, the age of the
study sample has consequences for both research design and
the conclusions that can be drawn.
What Do We Know from a Person’s Age?
All we know for sure from a person•s age is the year of birth
(birth cohort) and the historical time period of the person•s
development. This information has implications for the
intersection of lifecycle with sociohistorical events and
varies with gender, race, social class, and physical location.
Studies have often focused on cohort and aging effects, but
there has been a lack of focus on period effects that may ex-
plain observed age differences when examining the relation-
ship between health, behavior, and aging. Aperiod effect or is
a societal or cultural change that may occur between two
measurements that present plausible alternative explanations
for the outcome of a study (Baltes, Reese, & Nesselroade,
1988). This is particularly true for medical advances and
changes in treatments. For example, in the “eld of cardiol-
ogy, advances with surgery (i.e., stents) and new medications
have increased survival following a myocardial infarction,
but the increased number of persons surviving has resulted in
increased numbers of people with congestive heart failure.
The introduction of the prostate-speci“c antigen (PSA) test in
1987 accounts for age-related changes in the detection of
prostate cancer. At older ages, age does not provide the de-
velopmental benchmark that it does early in the lifecycle.
With increased age, there is also increased interindividual
differences such that the difference between two 10-year-olds
will be signi“cantly less than the dif ference between two
80-year-olds. Increased environmental exposure can in”u-
ence development in later life as can be seen when looking at
studies involving older twins (see McClearn & Heller, 2000).
Disease Prevalence in Aging
Disease prevalence has generally risen in the older noninsti-
tutionalized population (Crimmins & Saito, 2000). The
largest increases have been in heart disease and cancer, two
major causes of old-age mortality. Although prevalence has
increased, there has been a decline in mortality from heart
disease from the late 1960s through the present. Recently,
cancer mortality has also declined. The increased prevalence
of heart disease and cancer most likely results from mortality
declines and longer survival for people with these diseases
(Crimmins & Saito, 2000).
Older persons are more likely to have multiple disorders.
In 1987, 90 million Americans were living with chronic
conditions; 39 million of these were living with more than
one chronic condition. More than 45% of noninstitutional-
ized Americans have one or more chronic conditions
(Hoffman, Rice, & Sung, 1996). Among adults age 65 years
and older, the “ve most prevalent physician-diagnosed dis-
eases were hypertension (57%), diabetes (20%), coronary
artery disease (15%), cancer (9%), and cardiovascular dis-
ease (9%; Fillenbaum, Pieper, Cohen, Cornoni-Huntley, &
Guralnik, 2000). While the prevalence of diseases is increas-
ing, the rates of disability are declining (Manton & Gu,
2001)„these declines may be due to a better risk pro“le ear-
lier in the lifecycle. Future projections (Singer & Manton,
1998) suggest that this decline will continue.Age-Related Changes in FunctioningOlder persons are likely to have more sensory de“cits. Hear-
ing impairment is the third most common chronic condition
of older people, second only to arthritis and hypertension
(Fowles, 1994). More than 30% of noninstitutionalized indi-
viduals age 65 and older report problems with hearing, and
10% report problems with vision (USDHHS, 1994). Other
studies have found visual loss present in 13% of those
65 years and older and in 27% of those more than 85 years of
age (Havlik, 1986).
Not all physiological functions decline with age and not all
decline at the same rate. Age-related changes occur commonly
in pulse pressure, creatinine clearance, glucose tolerance,
body fat composition, and pulmonary vital capacity. All of
these may alter the effect of particular risk factors on cardio-
vascular outcomes as well as survivorship after disease onset,
and they may not all be accounted for in various population
studies (Kaplan, Haan, & Wallace, 1999). Overall, indepen-
dent of disease status, the older the organism, the longer it will
take to recover from a measured stress (Siegler, 1989).Defining Normal AgingHow do we differentiate aging and disease? This is one of the
most conceptually important questions in health psychology.
The de“nition is made dif “cult by the increasingly close
interrelationship between disease and aging. With advancing