Risk of depression in persons with Alzheimer's disease: A national cohort study

INTRODUCTION: Depression is a risk factor and possible prodromal symptom of Alzheimer's disease (AD), but little is known about subsequent risk of developing depression in persons with AD. METHODS: National matched cohort study was conducted of all 129,410 persons diagnosed with AD and 390,088 with all-cause dementia during 1998–2017 in Sweden, and 3,900,880 age- and sex-matched controls without dementia, who had no prior depression. Cox regression was used to compute hazard ratios (HRs) for major depression through 2018. RESULTS: Cumulative incidence of major depression was 13% in persons with AD and 3% in controls. Adjusting for sociodemographic factors and comorbidities, risk of major depression was greater than two-fold higher in women with AD (HR, 2.21; 95% confidence interval [CI], 2.11–2.32) or men with AD (2.68; 2.52–2.85), compared with controls. Similar results were found for all-cause dementia. DISCUSSION: Persons diagnosed with AD or related dementias need close follow-up for timely detection and treatment of depression. Highlights: In a large cohort, women and men with AD had >2-fold subsequent risk of depression. Risks were highest in the first year (>3-fold) but remained elevated ≥3 years later. Risk of depression was highest in persons aged ≥85 years at AD diagnosis. Persons with AD need close follow-up for detection and treatment of depression.