Objective: To investigate potential seasonal variation of migraine and other headaches in an Arctic population where light conditions are extreme during both winter and summer.
Background: Due to the immense seasonal variation in sunlight, focus on seasonal migraine variation in a population living in an Arctic area is interesting even from a theoretical point of view.
Methods: Northern Norway comprises the three Norwegian counties north of the Arctic Circle. There are three neurology centers in this region, which provide service for approximately half a million people. During a 2-year period, 1403 patients (0.3% of the population) were referred to these centers for a specialist assessment of their headache. A questionnaire was mailed to all these patients; the questionnaire included questions on headache characteristics to make it possible to identify migraine according to the International Headache Society criteria. Questions on seasonal variation of headache were also included.
Results: One thousand fifty-two patients (75%) returned the questionnaire. Nineteen percent reported that their headaches clearly did vary with season; 11% experienced more headache during polar night, while 7% had more symptoms during midnight sun season. When the migraine and nonmigraine groups were compared, significant differences were demonstrated. Patients with nonmigrainous headache were more likely to have increased headaches during the dark winter season, while patients with migraine experienced more headache during the summer (P =.002).
Conclusions: Patients with migraine were more likely to have headache during the bright Arctic summer season, and this distinguishes migraine from other headaches in this study. This observation may pertain to the increased light sensitivity and recently demonstrated cortical hyperexcitability in patients with migraine, and may perhaps suggest a role of the hypothalamus and/or melatonin secretion in migraine pathophysiology.