Seasonal and monthly patterns of relapses in adult MOG-IgG-associated disease (MOGAD): A retrospective analysis from Latin America

Introduction: Seasonality and monthly frequency of MOG-IgG-associated disease (MOGAD) relapses have not been reported in Latin America (LATAM), and limited data have been published worldwide. We aimed to investigate the seasonal and monthly distribution of MOGAD relapses in LATAM, evaluating potential temporal patterns and differences between first and subsequent relapses. Methods: This retrospective observational study analyzed relapse data from 117 LATAM MOGAD patients (Chile: 40, Peru: 30, Brazil: 22, Argentina: 14, Colombia: 8, and Ecuador: 3). All patients met the 2023 MOGAD criteria. The dataset included number of relapses, month of occurrence, and classification as first or subsequent relapse. Additional demographic and clinical characteristics were recorded. We applied Roger-modified Edward's and Rayleigh's tests for seasonality and Poisson regression analysis to calculate incidence rate ratios (IRRs) with 95 % confidence intervals (CIs) for relapses occurring in different months and seasons. Results: A total of 117 MOGAD patients experiencing 168 attacks (117 first attacks and 51 relapses) were included. Fewer relapses were observed in autumn (N = 21, 17 %; IRR 0.17, 95 % CI 0.11–0.25, p = 0.001), but no differences were found across the months when evaluating first attacks. A peak in relapse frequency was observed in November (N = 38, 23 %; IRR 0.13, 95 % CI 0.08–0.19, p = 0.01), but no significant differences were observed across the seasons when evaluating all relapses. Based on Roger-modified Edward's and Rayleigh's tests, neither first attacks nor subsequent relapses showed a statistically significant monthly or seasonal pattern. Conclusion: We were unable to detect a consistent monthly or seasonal pattern in MOGAD onset or relapses using circular statistics. These findings enhance our understanding of disease activity and may inform future research on external factors affecting relapse risk.