BACKGROUND: The temporal relationship between
the appearance of depressive symptoms and the clinical
onset of dementia and Alzheimer disease was evaluated
in a community sample.
METHODS: An original
sample of 1366 subjects aged 65 years or older,
selected randomly from a rural Pennsylvania community,
was cognitively screened at study entry and every 2
years thereafter. A subset of 954 survivors of this
cohort without dementia was screened for depressive
symptoms at the second and subsequent data-collection
waves. A "depression cluster" was identified by the
presence of 5 or more depressive symptoms, including
depressed mood, at the time of screening. Cognitively
impaired subjects and a sample of unimpaired controls
underwent standardized clinical evaluation to
determine the presence of incident dementia (by
DSM-III-R criteria) and probable or possible Alzheimer
disease (by criteria of the National Institute of
Neurological and Communicative Disorders and Stroke
and the Alzheimer's Disease and Related Disorders
Association) and to estimate the clinical onset of
dementia symptoms.
RESULTS: A highly increased
probability of the depression cluster developing
existed among subjects following the onset of dementia
(15.4% [6/39]) and Alzheimer disease (17.6% [6/34])
compared with subjects without dementia (3.2%
[23/712]). The odds ratios, after adjustment for age,
sex, education level, and self reported memory loss,
for the development of depression were 6.5 (95%
confidence interval, 2.2-19.1) in subjects with
Alzheimer disease and 5.2 (95% confidence interval,
1.8-15.2) in subjects with overall dementia.
Depressive symptoms did not confer a significantly
increased relative risk of dementia (1.27; 95%
confidence interval, 0.55-2.93) or Alzheimer disease
(1.28; 95% confidence interval, 0.51-3.20).
CONCLUSION: Depressive symptoms appeared to be
early manifestations, rather than predictors, of
Alzheimer disease in this community sample.