title: 24-hour distribution of migraine attacks.
abstract: BACKGROUND
  It is a widespread opinion that migraine attacks arise more frequently in the morning and that circadian rhythms may be responsible for the temporal pattern in migraine. However, only one small prospective study has previously been published on this topic.
  
  
  OBJECTIVE
  To investigate circadian variation in migraine.
  
  
  METHODS
  Eighty-nine females in fertile age who had participated in a previous questionnaire-based study volunteered to prospectively record in detail every migraine attack for 12 consecutive months. We reviewed all diary entries covering the period from March 2004 through April 2005, and did time-series analysis.
  
  
  RESULTS
  Fifty-eight patients had complete recordings over the 12 months and 26 completed the diaries for 1-11 months. Three patients were excluded due to missing data and 2 patients were excluded due to chronic migraine or medication-overuse headache. A total of 2314 attacks were experienced, in average 27.5 per patient (range 1-75). By fitting a sine curve to the data there was a harmonic trend with a peak around 13.40 and the peak/low ratio was 25.6 (95% CI: 8.3-78.6).
  
  
  CONCLUSIONS
  The main finding in our study is that migraine attacks tend to recur in a harmonic 24-hour cyclic manner with a peak around the middle of the day and that there is no difference between migraine with aura and migraine without aura regarding this.
authors.affiliation: Nordlandssykehuset--Neurology, Bodø, Norway.
authors.forename: Karl
authors.initials: K
authors.lastname: Alstadhaug
authors.forename: Rolf
authors.initials: R
authors.lastname: Salvesen
authors.forename: Svein
authors.initials: S
authors.lastname: Bekkelund
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008875:Middle Aged; D008881:Migraine Disorders / Q000453:epidemiology / Q000503:physiopathology*; D011446:Prospective Studies; D012189:Retrospective Studies; D013997:Time Factors