Depressive symptoms in oldest-old women: risk of mild cognitive impairment and dementia.

OBJECTIVES: Increasing evidence suggests that depression is a risk factor for cognitive impairment, but it is unclear if this is true among the oldest old. We determined whether elevated depressive symptoms predicted 5-year incident mild cognitive impairment (MCI) or dementia, and neuropsychological test performance among oldest-old women.
DESIGN: Prospective.
SETTING: Three study sites. PARTICIPANTS: 302 women ≥85 years (mean, 87 ± 2). MEASUREMENTS: Depressive symptoms were measured with the 15-item Geriatric Depression Scale (GDS); scores of 6 or more indicated elevated symptoms. Five years later, participants completed neuropsychological testing and clinical cognitive status was adjudicated.
RESULTS: In analyses of MCI versus normal cognition, 70% of women with GDS score 6 or more at baseline developed MCI versus 37% with GDS score less than 6. After adjustment for age, education, alcohol, and benzodiazepine use, and study site, GDS score 6 or more remained independently associated with much greater likelihood of developing MCI (multivariable odds ratio [MOR] = 3.71, 95% confidence interval (CI): 1.30-10.59). In analyses of dementia versus normal cognition, 65% of women with GDS score 6 or more developed dementia compared with 37% of those with GDS score less than 6 (MOR = 3.15, 95% CI: 1.03-9.65). Only 19% of women with GDS score 6 or more had normal cognitive status 5 years later, compared with 46% of those with GDS score less than 6 (MOR = 0.28, 95% CI: 0.11-0.73). Women with elevated depressive symptoms had worse scores on tests of global cognition and working memory.
CONCLUSION: Elevated depressive symptoms are an important risk factor for cognitive disorders and lower cognitive performance among women living to their ninth and tenth decades.