Objective: There is evidence that major depression increases the risk for dementia, but there is conflicting evidence as to whether depression may accelerate cognitive decline in dementia. The authors tested the hypothesis that decline in cognitive function over time is more pronounced in patients with dementia with comorbid depression, when compared with patients with dementia without depression history.
Design: Prospective, longitudinal cohort study of aging.
Setting: Nursing home.
Participants: Three hundred thirteen elderly nursing home residents (mean age at baseline: 86.99 years, standard deviation = 6.7; 83.1% women). At baseline, 192 residents were diagnosed with dementia, and another 27 developed dementia during follow-up. Thirty residents suffered from major depression at any point during the study, and 48 residents had a history of depression.
Measurements: The authors measured cognitive decline using change in Mini-Mental State Examination (MMSE) scores over up to 36 months. The authors calculated multilevel regression models to estimate the effects of age, gender, education, dementia status, depression, depression history, and an interaction between dementia and depression, on change in MMSE scores over time.
Results: Beyond the effects of age, gender, and education, residents showed steeper cognitive decline in the presence of dementia (β = -13.69, standard error = 1.38) and depression (β = -4.16, SE = 1.2), which was further accelerated by the presence of both depression and dementia (β = -2.72, SE = 0.65).
Conclusions: In dementia, the presence of depression corresponds to accelerated cognitive decline beyond gender and level of education, suggesting a unique influence of depression on the rate of cognitive decline in dementia.