Effects of socioeconomic status on mortality after Parkinson's disease: A nationwide population-based matched cohort study in Korean populations

Introduction To evaluate the mortality rate and impact of SES on mortality in PD using a nationwide cohort in Korea. Methods We selected patients diagnosed with PD (ICD-10 code: G20) and registration code for PD (V124) in the program for rare intractable diseases between 2004 and 2015. After that, atypical parkinsonism was excluded. A matched cohort of individuals without PD were enrolled by randomly matching patients by sex, age, and year of diagnosis to the PD group with a ratio of 1:9. Cox proportional hazard models were used to identify the effects of SES on mortality using Hazard Ratios and 95% confidence intervals. Results In total, 26,570 participants were enrolled. The mortality rate was 30.37% in PD cohort and 16.69% in the comparison cohort. According to income level, PD patients in low-middle group revealed significantly decreased HRs of 0.704 (95% CI, 0.533–0.930) compared to those in the lowest group. The medical aid group showed an increased mortality rate (HR = 1.552, 95% CI, 1.191–2.021) compared to the national health insurance group. In the subgroup analyses, medical aid was associated with mortality only in PD with female (HR = 1.740, 95% CI, 1.242–2.438) or aged 60–79 years (HR = 1.434, 95% CI 1.005–2.045). There was no significant difference in mortality rate according to residential area in PD. Conclusions In Korea, individual level low SES including income level and insurance type were significantly associated with increased mortality, whereas regional level SES (residential area) was not related with mortality on PD.