Neuromyelitis optica spectrum disorders relapses and seasonal influence in an equatorial country cohort.

Introduction: Information about seasonal distribution of Neuromyelitis optica spectrum disorders (NMOSD) attacks, particularly in tropical countries, has rarely been described and the reported data are diverse.

Objective: To evaluate influence of seasonal variation in NMOSD relapses in an equatorial country.

Patients and methods: Exploratory observational, retrospective ecological study in a cohort of patients with NMOSD followed from January 2008 to December 2019. Data of demographic, clinical information, characteristics of relapses and seasonal temporal variation were recorded. Also, the annual, monthly and intra-annual seasonal variation of relapses was quantified. A negative binomial regression was used to estimate the associations between the number of relapses and climatic and temporal variables.

Results: One hundred thirteen patients were included, most of them were female (89.38%), with a mean age at NMOSD diagnosis was 44.97 (±13.98) and the median of relapses per patient were 2 relapses (IQR 1-3). The patients presented 237 relapses, most of these in AQP4 seropositive patients (87.76%) and longitudinal extensive myelitis was the most frequent type of relapse (53.59%). According to the temporal variation, relapses were more common in the second rainy season (28.69%) during November and December. However, there weren't significant differences in the number of relapses between seasons and climatic variables in the multivariable model.

Conclusion: The number of NMOSD relapses in this equatorial country cohort did not exhibit any significant associations with climatic variations, including changes in rainy or dry seasons.