Epidemiological Characteristics of Subsyndromal Depression in Late Life

Abstract

Background: Subsyndromal depression is prevalent and associated with poor outcomes in late life, but its epidemiological characteristics have barely been investigated. The aim of this prospective cohort study is to compare the prevalence, incidence, and risk factors of subsyndromal depression with those of syndromal depression in community-dwelling elderly individuals. Methods: In a nationwide community-based study of randomly sampled Korean elderly population aged 60 years or older (N = 6,640), depression was assessed with standardized diagnostic interviews. At baseline and at 2-year and 4-year follow-ups, the authors diagnosed subsyndromal depression by the operational criteria and syndromal depression by the DSM-IV diagnostic criteria. Multivariate logistic regression analyses were conducted to identify the risk factors for incident depressive disorders. Outcomes: The age- and gender- adjusted prevalence rate of subsyndromal depression was 9·24% (95% CI = 8·54 – 9·93), which was 2·4-fold higher than that of syndromal depression. The incidence rate of subsyndromal depression was 21·70 per 1000 person-years (95% CI = 19·29 – 24·12), which was five-folds higher than that of syndromal depression. The prevalence to incidence ratio of subsyndromal depression was about half that of syndromal depression. The risk for subsyndromal depression was associated with female gender, low socioeconomic status, poor social support, and poor sleep quality while that of syndromal depression was associated with old age and less exercise. Interpretation: Subsyndromal depression should be validated as a clinical diagnostic entity, at least in late life, since it has epidemiological characteristics different from those of syndromal depression. Funding Statement: This study was supported by a grant from the Korean Health Technology R&D Project, Ministry for Health, Welfare, & Family Affairs, Republic of Korea (Grant No. A092077). Declaration of Interests: The authors declare that there are no conflicts of interest. Ethics Approval Statement: This study was approved by the Institutional Review Board of the Seoul National University Bundang Hospital.