title: Seasonal variation of migraine in an Arctic population.
abstract: OBJECTIVE
  To investigate seasonal variation of migraine headache in a population residing in an extreme Arctic locale.
  
  
  BACKGROUND
  Exposure to light may trigger migraine attacks and patients may also be hypersensitive to light between the attacks. In previous studies of migraine in Northern latitudes we have demonstrated that patients with migraine experience more attacks in the summer. In order to confirm this finding and gain more insight into a possible north-south effect of seasonal migraine variation, we performed a population-based study in Svalbard, which is one of the northernmost populated areas of the world.
  
  
  METHODS
  A postal questionnaire was mailed to all inhabitants aged 12 years or older living in Svalbard and the migraine diagnosis made by a structured telephone interview.
  
  
  RESULTS
  Of a total of 1569, 1029 (66%) returned the questionnaire. Of them, 184 (18%) experienced headache within the recent year prior to the study that could not be explained by alcohol, trauma, or viral infections. Eighty-eight individuals had migraine according to the revised criteria set by the International Headache Society. Nineteen (22%) reported seasonal variation of migraine. Ten (12%) experienced more migraine in the light season, while 9 (10%) got worse in the dark season. No differences in proportions of migraine with aura (MA) and migraine without aura (MO) could be detected. Also, the frequency of MA patients who used sunglasses to avoid migraine headache was nonstatistically increased compared with MO.
  
  
  CONCLUSIONS
  There was no indication of more seasonal variation of headache in a population of otherwise healthy people with migraine living in an extreme Arctic area with long periods of midnight sun and polar nights with complete darkness. The strength of conclusion, however, is significantly limited by a low response rate and small sample size.
authors.affiliation: Department of Neurology, Tromsø University Hospital, Tromsø, Norway.
authors.forename: Hallvard
authors.initials: H
authors.lastname: Lilleng
authors.forename: Svein
authors.initials: S
authors.lastname: Bekkelund
mesh_terms: D000328:Adult; D001110:Arctic Regions / Q000453:epidemiology*; D015331:Cohort Studies; D003624:Darkness; D004777:Environment; D005260:Female; D005843:Geography; D006801:Humans; D007407:Interviews as Topic; D008027:Light / Q000009:adverse effects*; D008297:Male; D008881:Migraine Disorders / Q000175:diagnosis / Q000453:epidemiology*; D010349:Patient Compliance; D018401:Sample Size; D012621:Seasons; D012647:Self-Assessment; D011795:Surveys and Questionnaires; D013538:Svalbard / Q000453:epidemiology*; D055815:Young Adult