Comorbidity increases the risk of relapse in multiple sclerosis

Objective:To evaluate the association between comorbidity and relapse rate in individuals with multiple sclerosis (MS).Methods:We recruited individuals with prevalent relapsing-onset MS from 4 Canadian MS Clinics to participate in a 2-year prospective multicenter cohort study involving cross-sectional assessment of comorbidities and relapses. Comorbidities were recorded using questionnaires, and relapses were captured from medical records at each visit. The association between comorbidities at baseline and relapse rate over the subsequent 2-year follow-up period was examined using Poisson regression, adjusting for age, sex, disability, disease duration, and treatment status.Results:Of 885 participants, 678 (76.6%) were women, averaging age 48.2 years at baseline. Anxiety (40.2%), depression (21.1%), hypertension (17.7%), migraine (18.1%), and hyperlipidemia (11.9%) were the most prevalent comorbidities. The frequency of participants experiencing relapses remained constant at 14.9% and 13.2% in years 1 and 2 post-baseline. After adjustment, participants reporting ≥3 baseline comorbidities (relative to none) had a higher relapse rate over the subsequent 2 years (adjusted rate ratio 1.45, 95% confidence interval [CI] 1.00–2.08). Migraine and hyperlipidemia were associated with increased relapse rate (adjusted rate ratio 1.38; 95% CI 1.01–1.89 and 1.67; 95% CI 1.07–2.61, respectively).Conclusions:Individuals with migraine, hyperlipidemia, or a high comorbidity burden (3 or more conditions) had an increased relapse rate over 2 years. These findings have potential implications for understanding the pathophysiology of MS relapses, and suggest that closer monitoring of individuals with specific or multiple comorbidities may be needed. Future research is needed to understand if the presence of comorbidity warrants a tailored approach to MS management.