Risk of Parkinson disease after depression: a nationwide population-based study.

Objective: To evaluate the risk of Parkinson disease (PD) among patients with depression by using the Taiwan National Health Insurance Research Database (NHIRD).

Methods: We conducted a retrospective study of a matched cohort of 23,180 participants (4,634 patients with depression and 18,544 control patients) who were selected from the NHIRD. Patients were observed for a maximum of 10 years to determine the rates of new-onset PD, and Cox regression was used to identify the predictors of PD. We also examined the risk of PD after excluding patients who were diagnosed with PD within 2 or 5 years after their depression diagnosis. A logistic regression model was used to identify risk factors associated with PD onset in patients with depression.

Results: During the 10-year follow-up period, 66 patients with depression (1.42%) and 97 control patients (0.52%) were diagnosed with PD. After adjusting for age and sex, patients with depression were 3.24 times more likely to develop PD (95% confidence interval 2.36-4.44, p < 0.001) compared with the control patients. After excluding patients who were diagnosed with PD within 2 or 5 years after their depression diagnosis, patients with depression had a higher hazard ratio for developing PD than the control patients. The odds ratios for age (1.09) and difficult-to-treat depression (2.18) showed that each is an independent risk factor for PD in patients with depression.

Conclusion: The likelihood of developing PD is greater among patients with depression than patients without depression. Depression may be an independent risk factor for PD.