Risk factors for COVID-19 infection in patients with multiple sclerosis: a nested case–control study

Background Risk factors for COVID-19 infection among people with multiple sclerosis (PwMS) remain unconfirmed. While biological, socioeconomic and clinical risk factors have been identified among the general population, a comprehensive assessment of risk factors for COVID-19 infection among PwMS is lacking. Methods A survey assessing personal experiences with COVID-19 in the USA was distributed online via the iConquerMS platform from December 18, 2020 to February 10, 2021. We conducted a retrospective nested case–control study of PwMS who self-reported testing positive for COVID-19 versus not. Risk factors evaluated include age, occupational setting, social determinants of health index, physical disability via Patient-Determined Disease Steps, disease-modifying therapy (DMT) and progressive disease. Results Of 611 PwMS, 47 (7.7%) self-reported a positive COVID-19 test. DMT use (odds ratio [95% CI]: 2.10 [0.75–5.39]) and employment outside the home (2.79 [1.42–5.41]) increased risk of COVID-19 infection, while older age (0.97 [0.95–0.99]), increased disability (0.81 [0.69–0.94]) and progressive disease (0.42 [0.19–0.86]) decreased risk in univariate analyses. No risk factor remained significant in the multivariate model. Of the 47 PwMS with a positive test, seven were admitted to the hospital, of whom two required intensive care. Forty-three (91.5%) experienced common COVID-19 symptoms, and 23 (48.9%) reported concurrent new/worsening neurological symptoms. Conclusion The prevalence of COVID-19 infection in this online study of PwMS approximated the US population's prevalence. When incorporating biological, socioeconomic and clinical risk factors for COVID-19, we did not find any independent risk factors for infection among PwMS in the USA.