Depression, Depression Treatments, and Risk of Incident Dementia: A Prospective Cohort Study of 354,313 Participants

The purpose of this study was to investigate the associations between courses of depression, the application of depression treatment, and the risk of incident dementia.In this prospective cohort study, 354,313 participants ages 50-70 years were recruited from the UK Biobank between 2006 and 2010 and were followed until 2020, with a total of 4,212,929 person-years. We initially studied the effect of depression on dementia incidence across 4 subgroups characterized by courses of depressive symptoms. Then, 46,820 participants with a diagnosis of depression were further categorized into treated and untreated groups. We compared the risk of dementia among different depression treatment groups in all participants who were depressed as well as 4 courses of depressive symptoms by performing survival analyses.Depression was associated with a 51% higher risk of dementia, among which the increasing, chronically high, and chronically low courses were associated with increased dementia risk, while no association was found in the decreasing course. Compared to those who were depressed but untreated, receiving depression treatments corresponded to a hazard ratio of 0.7 (95% CI, 0.62-0.77). Among the 3 detrimental courses, treatments for increasing and chronically low symptoms of depression were associated with a 32% and 28% lower risk of dementia, respectively, while the reduction effect for chronically high symptoms was insignificant.The negative association between depression treatment and incident dementia was significant in the increasing and chronically low courses, highlighting the necessity of timely interventional strategies before depression progresses to a chronically severe state.