The impact of PM2.5 on COVID-19 severity among Italian MS patients

Introduction: Studies have pointed out that air pollution longterm exposure may play a role in the severity and prognosis of SARS-CoV-2 infections. Additionally, air pollution has been associated to MS prevalence and course. However, the role of air pollution in COVID-19 severity has never been explored specifically among MS patients. Aims: To explore the association between air pollution assessed by PM2.5 levels and COVID-19 severity among MS patients. Methods: Demographic and clinical characteristics as well as data about Covid-19 severity were extracted from an Italian webbased platform (Musc-19 project) containing clinician-reported data from 118 Italian MS centers. PM2.5 ground-level concentrations were derived from air quality model results, as provided by the 'Copernicus Atmospheric Monitoring Service' (CAMS). Ordered logistic regression models were used to assess the association between PM2.5 (continuous and in tertiles) and Covid-19 prognosis (defined on three levels as mild course, hospitalization, and intensive care unit (ICU) admission or death) while controlling for possible confounders. Results: PM2.5 concentrations were available for 1517 MS patients, of whom 1321(87%) were classified as mild Covid-19 cases, 172(11%) were hospitalized and 24(2%) were admitted to ICU or died. Higher concentrations of PM2.5 were associated with increased odds of developing a worst Covid-19 prognosis (10-unit increase in PM2.5: OR(95% CI)=1.76(1.16-2.67) p-value=0.008;3rd vs 1st tertile: OR(95% CI)=1.74(1.17-2.59) p-value=0.006). Results remained consistent when we included only the Covid-19 cases confirmed by a nasopharyngeal swab (N=1087). Conclusions: Higher concentrations of PM2.5 are associated with Covid-19 severity among MS patients. Further studies are needed to evaluate the impact of other air pollutants, but urgent measures to reduce air pollution must be surely adopted.