Association between depression and the risk of Alzheimer's disease using the Korean National Health Insurance Service-Elderly Cohort.

In this cohort study, we assessed the association between depression and the risk of Alzheimer's disease from data obtained from the 2002 to 2013 Korean National Health Insurance Service-Elderly Cohort Database, which accounts for 10% of the South Korean population aged > 60 years. A total 518,466 patients were included in the analysis and followed up, unless they were excluded due to death or migration. Patients who sought treatment for depression or dementia within 1 year of the washout period and who were diagnosed with dementia within the 1-year period of the diagnosis of depression were excluded from the study. The risk of dementia was analysed using Cox proportional hazards models. Patients with a history of depression during the follow-up period were at a higher risk of Alzheimer's disease than those without a history of depression (HR 3.35, CI 3.27-3.42). The severe-depression group exhibited the highest risk of Alzheimer's disease (HR 4.41, CI 4.04-4.81), while the mild-depression group exhibited a relatively lower risk of Alzheimer's disease (HR 3.31, CI 3.16-3.47). The risk of Alzheimer's disease was associated with depression history and an increased severity of depression increased the risk of Alzheimer's disease.