Prevalence and incidence of depressive symptoms and diagnosis of depression as associated with elevated amyloid among Medicare beneficiaries with cognitive impairment.

Background: Depression and cognitive impairment commonly co-occur, and it has been hypothesized that the two share pathological processes. Our objective for this study was to determine the relationship between elevated β-amyloid level and the prevalence and incidence of depressive symptoms and diagnosed depression over two years among fee-for-service Medicare beneficiaries with cognitive impairment.

Methods: We utilized data from the CARE-IDEAS cohort study (N = 2078) including two measures of depressive symptoms (PHQ-2) and administrative claims data to identify pre-scan and incident depression diagnosis in subsample of fee-for-service Medicare beneficiaries (N = 1443). We used descriptive statistics and Poisson regression models with robust covariance.

Results: Beneficiaries whose scan results indicated not-elevated β-amyloid were significantly more likely to have been diagnosed with depression pre-scan (46.4 % vs. 33.1 %). There was no significant association between elevated amyloid and the incidence of depressive symptoms or diagnosed depression.

Limitations: The sample was limited to Medicare beneficiaries with cognitive impairment. Race/ethnic composition and education levels were not representative of the general population and there was substantial loss to follow-up. Mixed depressive / anxious episodes were captured as diagnoses of depression, potentially overestimating depression in this population.

Conclusions: There was a high prevalence and incidence of diagnosed depression in this cohort of Medicare beneficiaries, but the incidence of depressive symptoms and diagnosed depression was not associated with elevated β-amyloid.