AGING AND THE LIFE COURSEof shared history and cohort composition. Period
effects provide information about the effects of
contemporaneous events and situations on social
structure and individual behavior. Distinguishing
among age, period, and cohort effects also has
important implications for the generalization of
research results. Age effects are the same or highly
similar across time and place; thus, they are
generalizable. In contrast, cohort and period ef-
fects are, by definition, variable across time. Con-
sequently, generalization is limited.
Examination of age-period-cohort effects re-
quires large data bases in which multiple cohorts
are observed on multiple occasions over long peri-
ods of time. Because of these stringent require-
ments, few aging studies focus specifically on dis-
entangling these confounded factors. But recognition
of these sources of confounding appropriately
temper investigators’ generalizations. In addition,
this issue has sensitized researchers to the need to
examine change over time, with the result that
longitudinal studies have become the dominant
research design in efforts to characterize the aging
process.
No single theme nor easily summarized list of
topics does justice to the scope and diversity of
research on aging and the life course. However,
three major research domains can provide a gen-
eral sense of the current major avenues of aging
and life-course research: aged heterogeneity, life-
course dynamics, and life-course trajectories.
AGED HETEROGENEITYThe majority of research on older adults focuses
on heterogeneity in that population. In many ways,
this is the legacy of the problem orientation upon
which initial aging research in the social sciences
rested. Even now, most aging research focuses on
differences among older adults and the complex
configurations of social factors that can account
for individual differences during late life. And,
although there are many exceptions, a majority of
research in this domain focuses on the social
factors that explain individual behavior and per-
sonal well-being.
The specific topics that are examined in re-
search on aged heterogeneity are extensive. Health
and disability are major concerns in this research
tradition, including physical illness; mental illness,
especially depression; cognitive status and dement-
ing illness; functional status and disability; and
health behaviors. Health service utilization is a
corollary emphasis; there are numerous studies on
both utilization in general (e.g., doctors visits,
hospitalizations) and specialized health care set-
tings and providers (e.g., long-term care facilities,
emergency room visits, screening programs and
other preventative services, mental health profes-
sionals, dentists). There also has been extensive
research on the use of social and community
services and living arrangements—both of which
are strongly driven by health during late life.Along with health, socioeconomic status has
been a high-volume, long-standing focus in re-
search on aged heterogeneity. Economic status, in
the form of income and, to a lesser extent, assets
has been the primary emphasis of this research,
with studies of the antecedents and consequences
of retirement ranking as a close second. Pensions
have been shown to have strong effects upon the
adequacy of postretirement income, which has
spurred substantial investigation of the determi-
nants of pension acquisition and value.From a more social-psychological perspective,
there are strong research traditions examining
multiple psychosocial states that can be subsumed
under the umbrella of ‘‘quality of life.’’ Life satis-
faction and morale have received paramount at-
tention in this regard. But several dimensions of
the self (e.g., self-esteem, locus of control, sense of
mastery) also have rich research traditions.Two common elements of the wide range of
research conducted on the topic of aged heteroge-
neity merit note. First, a common thread in this
research is the desire to understand the processes
that render some older adults advantaged and
others disadvantaged. This is often described as
the ‘‘applied’’ character of aging research. Howev-
er, it also is a focus on stratification in the broadest
sense, which is one of the most persistent and
cherished issues in mainstream sociology. Research
on aging and the life course has contributed much
to our understanding of how broadly life chances
and life quality are linked to social factors, as well
as to the multiple powerful social bases of
stratification.Second, examination of heterogeneity among
the elderly has proven to be a strategic site for