Seasonal and Monthly Variation in Multiple Sclerosis Relapses: A Systematic Review and Meta-Analysis Publisher Pubmed



Nabizadeh F^{1, 2} ; Valizadeh P³ ; Yazdani Tabrizi M⁴ ; Moayyed K⁵ ; Ghomashi N⁶ ; Mirmosayyeb O⁷
Source: Acta Neurologica Belgica Published:2022

Abstract

Background: Multiple Sclerosis (MS) relapses are episodes of transient disease exacerbation. There are contradictory findings regarding seasonal variation in MS relapses. In this systematic review and meta-analysis, we aimed to investigate the seasonal and monthly variation in relapse rates among patients with MS. Methods: We systematically queried PubMed, Scopus, and Web of Science for published papers until February 30, 2022. Results: A total of 24 studies were included in this systematic review and meta-analysis with a total of 29,106 patients with MS. We found that the relapse rate was significantly lower in fall compared to the average relapse rate in other seasons with a risk ratio (RR) of 0.97 (95% CI 0.95–0.98). Furthermore, patients with MS experienced a higher number of relapses in April (RR: 1.06, 95% CI 1.01–1.11) and March (RR: 1.08, 95% CI 1.00–1.16) compared to other months. Also, the risk of relapse was lower in August (RR: 0.92, 95% CI.85–0.98), September (RR: 0.97, 95% CI.94–0.99), October (RR: 0.92, 95% CI.89–0.96), and November (RR: 0.93, 95% CI.89–0.97). Conclusion: Our systematic review and meta-analysis confirm the temporal fluctuations in the relapse of MS through a comprehensive review of the existing literature, with a lower relapse rate during late summer and fall and a higher relapse rate during early spring. © 2022, The Author(s) under exclusive licence to Belgian Neurological Society.