Oral contraceptives do not modify the risk of a second attack and disability accrual in a prospective cohort of women with a clinically isolated syndrome and early multiple sclerosis

Objective: To evaluate whether oral contraceptive (OC) use is associated with the risk of a second attack and disability accrual in women with a clinically isolated syndrome (CIS) and early multiple sclerosis (MS). Methods: Reproductive information from women included in the Barcelona CIS prospective cohort was collected through a self-reported cross-sectional survey. We examined the relationship of OC exposure with the risk of a second attack and confirmed Expanded Disability Status Scale of 3.0 using multivariate Cox regression models, adjusted by age, topography of CIS, oligoclonal bands, baseline brain T2 lesions, body size at menarche, smoking, and disease-modifying treatment (DMT). OC and DMT exposures were considered as time-varying variables. Findings were confirmed with sensitivity analyses using propensity score models. Results: A total of 495 women were included, 389 (78.6%) referred to ever use OC and 341 (68.9%) started OC before the CIS. Exposure to OC was not associated with a second attack (adjusted hazard ratio (aHR) = 0.73, 95% confidence interval (CI) = 0.33–1.61) or disability accrual (aHR = 0.81, 95% CI = 0.17–3.76). Sensitivity analyses confirmed these results. Conclusion: OC use does not modify the risk of second attack or disability accrual in patients with CIS and early MS, once considered as a time-dependent exposure and adjusted by other potential confounders.