Comparison of MS inflammatory activity in women using continuous versus cyclic combined oral contraceptives

Many women with multiple sclerosis (MS) report fluctuating symptoms across their menstrual cycle. Oral contraceptives (OCs) alter hormonal levels across the menstrual cycle. While cyclic OCs administer hormones for 21 days, followed by a week of placebo, continuous OCs can administer continuous doses of hormones for up to 3 months. Previous studies have suggested that OC use is associated with lower MS-related inflammation. We hypothesized that due to reduced hormonal fluctuations, women with MS might experience less inflammatory activity (clinical relapses+MRI) on continuous OCs than on cyclic OCs.

We performed a retrospective analysis of prospectively collected data. For women with MS aged 18-50 seen at the UCSF Center for MS and Neuroinflammation, we extracted data on OC use from the Electronic Medical Records (EMR). All variables were confirmed using manual clinical chart review. We identified 19 women with relapsing forms of MS on continuous OCs and matched them (2:1 when possible) to women on cyclic OCs for OC formulation, age, MS duration and DMT type. Inflammatory activity in the two groups was then compared using log-rank tests (time to new relapse, new T2-weighted lesion formation, and gadolinium-enhancing lesion formation) and t-tests (annualized relapse rate). We also performed subgroup analyses in women with at least 1 year (N = 28) and 2 years (N = 21) of clinical observation. A power calculation was performed.

There was no difference in time to relapse (p = 0.50) between continuous and cycling OC users. However, continuous OC users showed a statistical trend to longer time to T2 lesion formation (p = 0.09) and longer time to contrast-enhancing lesion formation (p = 0.05). In patients with at least 1 year of observation, there was a significant difference in time to T2 lesion formation (p = 0.03) and time to contrast-enhancing lesion formation (p = 0.02).

In this exploratory study, women on continuous OCs showed a trend towards less inflammatory activity on MRI relative to women on cyclic OCs. This difference was not reflected in relapse rates. We estimate that 342 patients would be required for an adequately powered cohort study to evaluate such an effect. Our findings provide reassurance that for women using continuous OCs to alleviate menstrual fluctuations in symptoms, there is not an increase in MS-related inflammatory activity.