To Örebro University

OBJECTIVE: To estimate risks for all-cause mortality and for severe COVID-19 in multiple sclerosis patients and across relapsing-remitting multiple sclerosis patients exposed to disease-modifying therapies.

METHODS: We conducted a Swedish nationwide population-based multi-register linkage cohort study and followed all multiple sclerosis patients (n = 17,692 in March 2020), individually age-, sex-, and region-matched to five population-based controls (n = 86,176 in March 2020) during March 2020-June 2021. We compared annual all-cause mortality within and across cohorts, and assessed incidence rates and relative risks for hospitalization, intensive care admission, and death due to COVID-19 in relation to disease-modifying therapy use, using Cox regression.

RESULTS: Absolute all-cause mortality among multiple sclerosis patients was higher from March to December 2020 than in previous years, but relative risks versus the population-based controls were similar to preceding years. Incidence rates of hospitalization, intensive care admission, and death due to COVID-19 remained in line with those for all-cause hospitalization, intensive care admission, and mortality. Among relapsing-remitting patients on rituximab, trends for differences in risk of hospitalization due to COVID-19 remained in the demographics-, socioeconomic status-, comorbidity-, and multiple sclerosis severity-adjusted model.

INTERPRETATION: Risks of severe COVID-19-related outcomes were increased among multiple sclerosis patients as a whole compared to population controls, but risk increases were also seen for non-COVID-19 hospitalization, intensive care admission, and mortality, and did not significantly differ during the pandemic compared to pre-pandemic years. The risk conveyed by disease-modifying therapies was smaller than previously assumed, likely as a consequence of the possibility to better control for confounders.