Spinal cord injury is related to an increased risk of multiple sclerosis: a population-based, propensity score-matched, longitudinal follow-up study.

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system (CNS). Trauma to the CNS has been postulated to play a role in triggering CNS autoimmune disease. Although the association between traumatic brain injury and MS has been suggested in previous studies, epidemiological data on the association between spinal cord injury (SCI) and MS is still lacking. The aim of the present population-based, propensity score-matched, longitudinal follow-up study was therefore to investigate whether patients with SCI were at a higher risk of developing MS. A total of 11,913 subjects ages between 20 and 90 years with at least two ambulatory visits with the principal diagnosis of SCI in 2001 were enrolled in the SCI group. We used a logistic regression model that included age, sex, pre-existing comorbidities, and socioeconomic status as covariates to compute the propensity score. The non-SCI group consisted of 59,565 propensity score-matched, randomly sampled subjects without SCI. Stratified Cox proportional hazard regression with patients matched by propensity score was used to estimate the effect of SCI on the risk of developing subsequent MS. During follow-up, five subjects in the SCI group and four in the non-SCI group developed MS. The incidence rates of MS were 17.60 (95% confidence interval [CI], 5.71-41.0) per 100,000 person-years in the SCI group and 2.82 (95% CI, 0.77-7.22) per 100,000 person-years in the non-SCI group. Compared with the non-SCI group, the hazard ratio of MS for the SCI group was 8.33 (95% CI, 1.99-34.87, p=0.0037). Our study therefore shows that patients with SCI have an increased risk of developing MS.