Clinical and demographic characteristics of male MS patients included in the national registry-RelevarEM. Does sex or phenotype make the difference in the association with poor prognosis?

Background : In multiple sclerosis demographics there is a well-known female prevalence and male patients have been less specifically evaluated in clinical studies, though some clinical differences have been reported between sexes. Objective : The objective of this study was to assess clinical and demographic differences between male and female patients included in the national Argentine MS Registry – RelevarEM. Material and methods : This study was observational, retrospective, and was based on the data of 3,099 MS patients included as of 04 April 2021. The statistical analysis plan included bivariate analyses with the crude data and also after adjustment for the MS phenotype, further categorized as progressive-onset MS or relapsing-onset MS. In the adjusted analysis, the Mantel-Haenszel odds ratio was compared to the crude odds ratio, to account for the phenotype as a confounder. Results : The data from 1,074 (34.7%) men and 2,025 (65.3%) women with MS diagnosis were analysed. Males presented primary progressive disease two times more often than women (11% and 5%, respectively). In the crude analyses by sex, the presence of exclusively infratentorial lesions in the magnetic resonance imaging studies was more frequent in males than in females, but after adjustment by MS onset phenotype, such difference was only present in males with relapsing-onset MS (p = 0.00006). Similarly, worse Expanded Disability Status Scale scores were confirmed only in men with relapsing-onset disease after phenotype adjustment (p = 0.02). Conclusion : We did not find any statistically significant clinical or demographic difference between sexes when the progressive or remitting MS phenotype was specifically considered. However, the differences we found between the clinical phenotypes are in line with the literature and highlight the importance of stratifying the analyses by sex and phenotype when designing MS studies.