Sex impacts treatment decisions in multiple sclerosis.

Background: Individual disease-modifying treatment (DMT) decisions might differ between female and male people with MS (pwMS).

Objective: To identify sex-related differences in DMT strategies over the past decades in a real-world setting.

Methods: In this cohort study, data from the Austrian Multiple Sclerosis Treatment Registry (AMSTR), a nationwide prospectively collected registry mandatory for reimbursement, were retrospectively analyzed. Of 4840 pwMS, those with relapsing-remitting MS, aged at least 18 years, who started DMT and had at least two clinical visits, were identified. At baseline, demographics, Expanded Disability Status Scale (EDSS) score, annualized relapse rate (ARR) in the prior 12 months and MRI lesion load were assessed. At follow-up, ARR, EDSS scores, and DMT were determined.

Results: A total of 4224 pwMS were included into the study and had a median of 10 (IQR 5-18) clinical visits over an observation period of 3.5 (IQR 1.5-6.1) years. Multivariable Cox regression analysis revealed that the probability of DMT escalation due to relapse activity was lower in female than male pwMS (HR 4.1 vs. 8.3 per ARR). Probability of discontinuing moderate-effective DMT was higher in female pwMS when they were younger (HR 1.03 per year), and lower in male pwMS at higher age (HR 0.92). Similarly, female pwMS were more likely to stop highly effective DMT than male pwMS (HR 1.7). Among others, the most frequent reason for DMT discontinuation was family planning in female pwMS. All sex-related effects were independent of disease activity, such as MRI lesion load, baseline ARR or EDSS.

Conclusions: Real-world treatment decisions are influenced by sex-related aspects. Awareness of these associations should prevent unwarranted differences in MS care.