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.