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

Abstract 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.