Cumulative exposure to estrogen may increase the risk of migraine in women.

Background: Migraine is a common disorder, particularly affecting women during their reproductive years. This female preponderance has been linked to exposure to female sex hormones.

Methods: We used self-reported data from women born in 1943-1965 enrolled in the Norwegian Women and Cancer Study to examine the differences between women with migraine and women without migraine in a prospective design with respect to both endogenous and exogenous female sex hormone exposure.

Results: In total, 62,959 women were included in the study, of whom 24.8% reported previous migraine (n = 15,635). Using a Cox proportional hazards model, we found that higher age at menarche reduced the risk of migraine (hazards ratio (HR) = 0.96, 95% confidence interval (CI) = 0.95-0.98) and that oral contraceptive use and parity increased the risk of migraine (HR = 1.12, 95% CI = 1.06-1.18 and HR = 1.37, 95% CI = 1.29-1.46, respectively).

Conclusions: Older age at menarche appears to reduce migraine risk, whereas oral contraceptive use and having children appear to increase the risk. Further research is required to investigate the causality of these associations.