The temporal association between incident late-life depression and incident dementia.

Abstract

There is an established association between depression and subsequent dementia. The present study examined temporal associations between incident late-life depression and subsequent dementia, also considering age and sex. We used longitudinal health claims data from the largest German health insurance provider ('Allgemeine Ortskrankenkasse') considering up to 9 follow-up years in piecewise exponential models. ICD-10 codes were used to define incident depression and dementia in individuals ≥65years (n=97110). Incident depression was associated with a higher risk of subsequent dementia (incidence rate ratios (IRR) adjusted for age and sex: IRR=1.58, 95% CI=1.51-1.64). The strongest association was found for the shortest interval of 1 quarter (IRR=2.04, 95% CI=1.88-2.21), with significant associations up to an interval of roughly 3years. The association was more pronounced and lasted for more quarters in the younger portion of this study group (ages from 65-74: IRR=2.00, 95% CI=1.83-2.18; 75-84: IRR=1.64, 95% CI=1.55-1.73; ≥85: IRR=1.19, 95% CI=1.08-1.31). It was stronger among men than women (men: IRR=1.98, 95% CI=1.84-2.14; women: IRR=1.44, 95% CI=1.37-1.51) with no sex-specific temporal association. This large claims data study confirmed that incident late-life depression is associated with a higher risk of dementia within the 3years following diagnosis. Hence, incident late-life depression should prompt further cognitive examinations and referrals to specialists. This might apply especially to younger seniors and men.