Spinal cord injury and Parkinson's disease: a population-based, propensity score-matched, longitudinal follow-up study

Objectives: To investigate whether patients with spinal cord injury (SCI) are at an increased risk of developing Parkinson's disease (PD). Study design: A population-based, propensity score-matched, longitudinal follow-up cohort study. Setting: The study was conducted using the National Health Insurance (NHI) Research Database. Methods: A total of 10 125 patients with at least 2 ambulatory visits with a diagnosis of SCI in 2001 were enrolled in the SCI group. The non-SCI group comprised 10 125 propensity score-matched patients without SCI. The propensity scores were computed using a logistic regression model that included age, sex, comorbidities and socioeconomic status. The PD-free survival rates of the two groups were estimated using the Kaplan-Meier method. Stratified Cox proportional hazard regression was used to estimate the effect of SCI on subsequent occurrence of PD. Results: During the 3-year follow-up period, 99 subjects in the SCI group and 59 in the non-SCI group developed PD. The hazard ratio of PD for the SCI group compared with the non-SCI group was 1.65 (95% confidence interval 1.16-2.33, P=0.0049). The PD-free survival rate for the SCI group was lower than that for the non-SCI group (P=0.0017). Conclusions: This study shows that SCI is associated with a subsequent increased risk of PD. Further studies are needed to elucidate the mechanism underlying this association.