Circadian rhythms and migraine.

To determine whether migraine exhibits a circadian rhythm or occurs randomly throughout the day, we analyzed the time of migraine onset in 15 migraine suffers (migraineurs) over 20 weeks. The patients suffered 211 migraine attacks over 20 weeks (range 3 to 30, median 13). Twelve of the 15 migraineurs had 50% or more of headache onsets during a 4-hour block of time. As a group, the migraineurs showed a circadian variation in migraine onset, with a marked increase in attacks between 6 AM and 8 AM, peak frequency of migraine onset between 8 AM and 10 AM, and a dramatic decrease in frequency between 8 PM and 4 AM. The circadian rhythm of migraine onset parallels that of myocardial infarction, platelet aggregability, plasma cortisol, and plasma catecholamines. These associations suggest that alteration of vasomotor tone may be involved in the initiation of migraine attacks.