No association between oral contraceptive exposure and subsequent MS: A population-based nested case-control study in primary care.

Background: Conflicting data exist around oral contraceptive exposure and subsequent multiple sclerosis (MS).

Objective: To use routinely collected primary healthcare data to explore the potential association between oral contraceptive exposure and subsequent MS in females at population level.

Methods: We performed a nested case-control study using electronic primary care data, with complete electronic ascertainment from 1990. Logistic regression was used to evaluate associations between contraceptive exposure and MS, without and with adjusting for age, ethnicity and deprivation.

Results: A total of 4455 females were included: 891 cases and 3564 controls. No association was seen between oral contraceptive exposure and subsequent MS, or between any contraceptive, combined oral contraceptive pill (COCP) or progesterone-only pill (POP) use 0-2, 2-5 or >5 years prior to MS. Conclusions: In the largest population-based study to date, we find no evidence of an association between oral contraceptive exposure and subsequent MS diagnosis.