Association between multiple sclerosis and the risk of stroke: A population-based retrospective cohort study

Background and Objectives: Previous studies addressing the association between multiple sclerosis (MS) and stroke yielded conflicting results. The current study aimed to evaluate the association between MS and incident stroke, overall and by main stroke subtypes. Methods: We conducted a population-based retrospective cohort study utilizing the Clalit Health Services database, the largest healthcare provider in Israel. The cohort included all incident MS patients aged ≥25 years diagnosed between 1 January 2005 and 31 December 2022. Each MS patient was matched to 10 non-MS controls based on age, sex, and population sector. MS cases (exposed group) and non-MS cases (unexposed group) were followed from the index date until 31 December 2023 for stroke occurrence. Results: The study included 1602 MS patients and 16,020 non-MS controls. Overall stroke was diagnosed in 26 patients in the MS group and 233 in the non-MS group, reflecting a crude incidence rate of 1.61 and 1.40 per 1000 person-years, respectively. The adjusted hazard ratios (HRs) were 0.95 (95 % CI, 0.61–1.48) for overall stroke, 0.94 (95 % CI, 0.59–1.51) for ischemic stroke, and 0.94 (95 % CI, 0.25–3.56) for intracerebral hemorrhage. The results remained consistent when analysis was restricted to patients without a prior history of stroke, when follow-up was restricted to 2 years, and when the cohort was extended to include preexisting MS cases. Age and sex did not modify the association between MS and stroke risk (p-for interaction=0.161 and 0.647, respectively). Conclusions: Our findings suggest that MS is not associated with an increased risk of stroke.