Recurrent depressive symptoms and the incidence of dementia and mild cognitive impairment.
OBJECTIVE
A history of depression has been linked to an increased dementia risk. This risk may be particularly high in recurrent depression due to repeated brain insult. We investigated whether there is a dose-dependent relationship between the number of episodes of elevated depressive symptoms (EDS) and the risk for mild cognitive impairment (MCI) and dementia.


METHODS
A total of 1,239 older adults from the Baltimore Longitudinal Study of Aging were followed for a median of 24.7 years. Diagnoses of MCI and dementia were made based on prospective data. Participants completed the Center for Epidemiologic Studies Depression Scale at 1- to 2-year intervals and were considered to have an EDS if their score was > or = 16. Kaplan-Meier survival curves, log-rank test for trend for survivor functions, and Cox proportional hazards models were conducted to examine the risk of MCI and dementia by number of EDS.


RESULTS
We observed a monotonic increase in risk for all-cause dementia and Alzheimer disease as a function of the number of EDS. Each episode was associated with a 14% increase in risk for all-cause dementia. Having 1 EDS conferred an 87%-92% increase in dementia risk, while having 2 or more episodes nearly doubled the risk. Recurrence of EDS did not increase the risk of incident MCI.


CONCLUSIONS
Our findings support the hypothesis that depression is a risk factor for dementia and suggest that recurrent depression is particularly pernicious. Preventing the recurrence of depression in older adults may prevent or delay the onset of dementia.
Dotson
Vonetta M
VM
National Institute on Aging, NIA/NIH/IRP, Baltimore, MD, USA. vonetta@phhp.ufl.edu
Beydoun
May A
MA
Zonderman
Alan B
AB
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000523:psychology; D003072:Cognition Disorders / Q000150:complications / Q000453:epidemiology* / Q000523:psychology*; D003704:Dementia / Q000150:complications / Q000453:epidemiology* / Q000523:psychology*; D003863:Depression / Q000150:complications / Q000517:prevention & control / Q000523:psychology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D055502:Secondary Prevention