Effects of COVID-19 Infection on Symptom Severity and Disability in Multiple Sclerosis.

Background and objectives: Infections, including infection with SARS-CoV-2 (COVID-19), could alter the course of multiple sclerosis (MS). Previous studies assessing the effects of COVID-19 on MS outcomes were small and had discordant findings. The study objective was to evaluate the association of COVID-19 infection with changes in the trajectory of MS symptoms and disability.

Methods: We used a controlled interrupted time series (ITS), a quasiexperimental study design using longitudinal data from the North American Research Committee on Multiple Sclerosis Registry. Participants who completed at least 3 surveys before and after their index survey were identified. Exposure of interest was COVID-19 infection based on confirmed diagnosis using an at-home or laboratory test, as reported by the participant. Symptoms were measured using the SymptoMScreen (SMSS), a self-report measure of symptom severity across 12 domains common in MS. Disability was measured using PDDS. Segmented regression was used to compare changes in outcomes over time between cohorts, before and after the exposure (COVID-19 infection).

Results: The spring 2023 survey response rate was 67.3%, and 4,787 participants completed the COVID-19 questions. Of those participants, 2,106 (44.0%) reported ever having confirmed COVID-19. The COVID-19 infection cohort included 796 participants with ≥3 surveys both before and after index survey. The uninfected cohort included 1,534 participants (32.0%) who reported never having COVID-19 nor other infections in the previous 6 months, of whom 1,336 had the requisite number of presurveys and postsurveys. After adjusting for participant characteristics, the SMSS score increased nominally over time in the COVID-19 and uninfected cohorts and this change over time did not differ between cohorts either before (0.005, 95% CI -0.025 to 0.035) or after (-0.0002, 95% CI -0.014 to 0.014) COVID-19 infection. The immediate effect of COVID-19 infection on the SMSS total score was minimal within the COVID-19 cohort and did not differ between cohorts (0.41, 95% CI -0.13 to 0.94). Findings were similar for disability.

Discussion: Our study using an ITS design found that COVID-19 infection was not associated with immediate changes in symptom severity or disability, nor did it change the trajectories of these outcomes over a median follow-up of 18 months. Although results may not generalize to younger people with MS, these findings enhance our general understanding of the consequences of infection in people with MS.