Seasonality of attacks of MOG antibody-associated disease in the UK

<h3>Background</h3> MOG antibody-associated disorder (MOGAD) is an autoimmune CNS disease with phenotypic and radiological similarities to MS. The most common manifestations are optic neuritis in adults and ADEM in children. Half paediatric ADEM cases are associated with MOG antibodies. Both ADEM and MS demonstrate seasonal peaks. Although some studies have demonstrated seasonal fluctuations in MOGAD attacks they often lack power and statistical validity. <h3>Aims</h3> Primary outcomes were seasonality of total attacks and of onset attacks. Exploratory analyses included effect of season on frequency of attacks in children ≤ 12 years old and on ADEM/ADEM-like attacks <h3>Methods</h3> We identified MOGAD attacks occurring between 2010 and 2021 from a large national database. Attack date and phenotype and age at attack were extracted. Edwards’ test was applied to detect deviation from a uniform monthly distribution. <h3>Results</h3> We analysed 439 attacks from 248 patients. Neither total nor onset attacks demonstrated significant seasonal variation. Exploratory analyses of paediatric attacks and ADEM/ADEM-like attacks did not show any effect of season. <h3>Discussion</h3> This large study using robust statistical methods refutes the apparent seasonality of MOGAD attacks observed in smaller cohorts. International collaborations are needed to confirm the generalisability of this finding to other latitudes.