Background: Migraine is three times more common in women than men. There is a clinical impression that migraines are more common and severe around the time of menses. Objectives: To determine 1) the distribution of headache attacks by day of the menstrual cycle in women with migraine, 2) if the excess occurrence varies by headache type, and 3) if headache features differ by time in the menstrual cycle. Methods: In a population-based sample, 81 menstruating women with clinically diagnosed migraine were enrolled in a 98-day diary study and completed a total of 7219 diary days. The daily diary was used to record the occurrence of menses, headache days, and, on days with headache, associated headache features (i.e., symptoms, quality-of-pain, attack duration, pain intensity, and disability at work, household work, and nonwork activities). Results: An excess risk of headache occurred perimenstrually and was highest on days 0 and 1 of the cycle (day 0 being the first day of menses). A significantly elevated risk of headache on days 0 and 1 was observed for migraine without aura (OR 2.04; 95% CI 1.49, 2.81) and for tension-type headache (OR 1.67; 95% CI 1.24, 2.25). Elevated risks were also observed in the 2 days before onset of menses for migraine without aura (OR 1.80; 95% CI 1.40, 2.30). A significantly lower risk was observed around the time of ovulation for all headaches (OR 0.44; 95% CI 0.27, 0.72). Few significant differences were observed in headache features (i.e., pain intensity, disability score, symptom score, headache duration) by day of the cycle overall or by headache type. Pain intensity was slightly greater for migraine headaches during the first 2 days of menses. Conclusions: Attacks of migraine without aura, but not migraine with aura, were more likely to occur 2 days before onset of menses and on the first 2 days of menses. This study does not support the clinical notion that headaches, regardless of type, are more severe during the perimenstrual period compared to other times in the cycle. Although migraine headaches are significantly more painful during the first 2 days of menses, differences are small.–1523

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