COVID-19 Severity in Multiple Sclerosis: Putting Data Into Context

Abstract

Background and objectives: It is unclear how multiple sclerosis (MS) affects the severity of COVID-19. The aim of this study is to compare COVID-19-related outcomes collected in an Italian cohort of patients with MS with the outcomes expected in the age- and sex-matched Italian population.

Methods: Hospitalization, intensive care unit (ICU) admission, and death after COVID-19 diagnosis of 1,362 patients with MS were compared with the age- and sex-matched Italian population in a retrospective observational case-cohort study with population-based control. The observed vs the expected events were compared in the whole MS cohort and in different subgroups (higher risk: Expanded Disability Status Scale [EDSS] score > 3 or at least 1 comorbidity, lower risk: EDSS score ≤ 3 and no comorbidities) by the χ² test, and the risk excess was quantified by risk ratios (RRs).

Results: The risk of severe events was about twice the risk in the age- and sex-matched Italian population: RR = 2.12 for hospitalization (p < 0.001), RR = 2.19 for ICU admission (p < 0.001), and RR = 2.43 for death (p < 0.001). The excess of risk was confined to the higher-risk group (n = 553). In lower-risk patients (n = 809), the rate of events was close to that of the Italian age- and sex-matched population (RR = 1.12 for hospitalization, RR = 1.52 for ICU admission, and RR = 1.19 for death). In the lower-risk group, an increased hospitalization risk was detected in patients on anti-CD20 (RR = 3.03, p = 0.005), whereas a decrease was detected in patients on interferon (0 observed vs 4 expected events, p = 0.04).

Discussion: Overall, the MS cohort had a risk of severe events that is twice the risk than the age- and sex-matched Italian population. This excess of risk is mainly explained by the EDSS score and comorbidities, whereas a residual increase of hospitalization risk was observed in patients on anti-CD20 therapies and a decrease in people on interferon.

Figure 1. Observed Hospitalizations, ICU Admissions, and Deaths in the MuSC-19 Cohort and Age-Sex–Matched Italian Population

Observed hospitalizations, ICU admissions, and deaths in the MuSC-19 cohort (n = 1,362) as compared to the expected number of events in an age and matched cohort from the Italian population. ICU = intensive care unit; RR = risk ratio.

Figure 2. Observed and Expected Hospitalizations, ICU Admissions, and Deaths in Lower-Risk (A) and Higher-Risk (B) Patients

Observed hospitalizations, ICU admissions, and deaths in the lower-risk patients (A; EDSS score ≤ 3 and no comorbidities, n = 809) and in the higher-risk patients (B; EDSS score > 3 or comorbidities, n = 553) as compared to the expected number of events in the age and matched cohort from the Italian population. EDSS = Expanded Disability Status Scale; ICU = intensive care unit; RR = risk ratio.

Figure 3. Observed and Expected Hospitalizations, ICU Admissions, and Deaths According to DMT and Lower-Risk (A) and Higher-Risk (B) Groups

Observed hospitalizations, ICU admissions, and deaths in the lower-risk patients (EDSS score ≤ 3 and no comorbidities, n = 809) and in the higher-risk patients (EDSS score > 3 or comorbidities, n = 553) according to the DMT taken as compared to the expected number of hospitalizations in the age- and sex-matched sample from the Italian population. In the interferon group, the RR = 0 because there were no observed events. DMT = disease-modifying therapy; EDSS = Expanded Disability Status Scale; ICU = intensive care unit; IFN = interferon; RR = risk ratio.