Patients with multiple sclerosis: COVID-19 related disease activity and hospitalisations based on a nationwide cohort study.

BACKGROUND

It has not previously been clarified if COVID-19 triggers disease activity and increases the risk of hospitalisation with COVID-19 in patients with multiple sclerosis. We examined the association between COVID-19 and the use of systemic corticosteroids prescriptions and hospital contacts at neurological departments as proxies of disease activity among patients with multiple sclerosis. Furthermore, we examined whether patients with multiple sclerosis were more likely to be hospitalised with COVID-19 compared to references.

METHODS

This study was based on nationwide health registries with data on the Danish population of 2,222,946 individuals with a positive COVID-19 PCR test. To study disease activity our study population consisted of all patients with multiple sclerosis and a positive COVID-19 PCR test. Our proxies for disease activity were compared after versus before a positive COVID-19 PCR test using a binomial regression model. Adjustments were made for age, sex, comorbidity, length of multiple sclerosis diagnosis, calendar period, vaccination, and immunomodulatory treatment. To study the risk of hospitalisation with COVID-19 in patients with multiple sclerosis our study population here consisted of all Danish citizens with a COVID-19 positive PCR test. In logistic regression models we estimated odds ratio (OR) for hospitalisation with COVID-19 in patients with multiple sclerosis relative to patients affected with other autoimmune diseases (inflammatory bowel disease/rheumatoid arthritis), and relative to individuals from the general population. Adjustments were made for age, sex, comorbidity, vaccination, and calendar period. To examine the impact of disease-modifying treatment, the risk of hospitalisation with COVID-19 was estimated in those with disease-modifying treatment versus those without any disease-modifying treatment.

RESULTS

We included 7358 patients with multiple sclerosis and a positive COVID-19 PCR test. The adjusted incidence rate ratio (aIRR) for having corticosteroid prescriptions after COVID-19 in patients with multiple sclerosis was 0.93 (95 % CI 0.78 - 1.10), and the aIRR for hospital contacts at neurological departments/admissions with multiple sclerosis as primary diagnosis after COVID-19 infection was 1.10 (95 % 1.00-1.22). Adjusted OR (aOR) for hospitalisation with COVID-19 in the 30 days after a positive COVID-19 PCR test was 3.21 (95 % CI 2.75-3.74) compared to patients with other autoimmune diseases and the aOR was 5.34 (95 % CI 4.65-6.14) for patients with multiple sclerosis compared to all other individuals in the general population with a positive test. We found no increased risk of hospitalisations with COVID-19 in patients with multiple sclerosis using disease-modifying treatment 6 months prior to a positive COVID-19 PCR test compared to patients with multiple sclerosis without disease-modifying treatment (aOR 0.94 (95 % CI 0.69-1.27)).

CONCLUSIONS

In this nationwide cohort of patients with multiple sclerosis, COVID-19 did not seem to trigger multiple sclerosis disease activity (based on proxy variables). We found a significantly increased risk of being hospitalised with COVID-19 in the first 30 days after a positive COVID-19 PCR test in patients with multiple sclerosis irrespective of the type of reference population. In patients with multiple sclerosis, the use of disease-modifying treatment did not increase the risk of hospitalisation with COVID-19.