Association between depression and risk of Parkinson's disease in South Korean adults

Background: Depression is considered a predictive factor for cognitive impairments. At the same time, Parkinson's disease (PD) is a growing public health problem. The aim of this study is to examine the association between depression and PD risk among South Korean adults. Methods: Data from 21,766 participants aged over 40, derived from the National Health Insurance Service National Sample Cohort (2002-2013), were included. Propensity score matching (1:1) was used to match participants with and without depression (case: 10,875, control: 10,875). The dependent variable was PD risk. A Cox proportional hazards regression model was built to analyze the associations between variables. Results: People with depression had a higher risk of PD than those without depression (hazard ratio (HR) = 1.61, 95% confidence interval (CI) = 1.26-2.06). Among individuals with disabilities, those with depression had a higher risk of PD (HR = 2.31, 95% CI = 1.08-4.94). According to the Charlson Comorbidity Index (CCI) score, those with depression had a higher risk of PD than their counterparts (CCI score >= 5: HR = 1.63, 95% CI = 1.21-2.20). Limitations: The limitations include the inability to 1) explore factors such as smoking and drinking status, which could be related to PD risk and 2) identify undiagnosed PD that already existed at the time of diagnosis of depression. Conclusions: The results suggest that having depression places individuals at a higher risk of PD. Interventions to alleviate the risk of PD should focus on adequate depression management.