Comorbidity and Disease Activity in Multiple Sclerosis.

Importance: Multiple studies suggest that comorbidity worsens clinically relevant outcomes in multiple sclerosis (MS), including the severity of disability at diagnosis and rate of disability worsening after diagnosis. However, less is known regarding the association of comorbidity with measures of disease activity, such as relapse rate and magnetic resonance imaging lesion accrual, which are relevant to clinicians and clinical trialists. Objective: To evaluate the association of comorbidities with disease activity in clinical trials of disease-modifying therapies (DMTs) in populations with MS. Design, Setting, and Participants: A 2-stage meta-analytic approach was used in this cohort study of individual participant data from phase 3 clinical trials of MS DMTs that had 2 years of follow-up and were conducted from November 2001 to March 2018. Data were analyzed from February 2023 to June 2024. Exposure: Comorbidity burden and individual comorbidities present at trial enrollment, including hypertension; hyperlipidemia; functional cardiovascular disease, ischemic heart, cerebrovascular, and peripheral vascular disease; diabetes; autoimmune thyroid and miscellaneous autoimmune conditions; migraine; lung and skin conditions; depression; anxiety; and other psychiatric disorders. Main Outcomes and Measures: The main outcome was evidence of disease activity (EDA) over 2 years of follow-up, defined as confirmed relapse activity, disability worsening, or any new lesions on magnetic resonance imaging. Results: A total of 16 794 participants with MS were included from 17 clinical trials (67.2% female). Over the 2-year follow-up, 61.0% (95% CI, 56.2%-66.3%; I2 = 97.9%) of the pooled trials had EDA. After adjusting for multiple factors, the presence of 3 or more comorbidities was associated with an increased hazard of EDA (adjusted hazard ratio [AHR], 1.14; 95% CI, 1.02-1.28) compared with no comorbidity. Presence of 2 or more cardiometabolic conditions was also associated with an increased hazard of EDA (AHR, 1.21; 95% CI, 1.08-1.37) compared with no cardiometabolic comorbidity. Presence of 1 psychiatric disorder was associated with an increased hazard of EDA (AHR, 1.07; 95% CI, 1.02-1.14). Conclusions and Relevance: In this study, a higher burden of comorbidity was associated with worse clinical outcomes in people with MS, although comorbidity could potentially be a partial mediator of other negative prognostic factors. Our findings suggest a substantial adverse association of the comorbidities investigated with MS disease activity and that prevention and management of comorbidities should be a pressing concern in clinical practice.