Photophobia and Seasonal Variation of Migraine in a Subarctic Population.

OBJECTIVE: To investigate associations between photophobia and seasonal variation of migraine.

METHODS: In this cross-sectional study, migraineurs consecutively recruited were referred to a specialist center located above the Arctic Circle at 68-71 degrees North during a 2.5-year period. Data were obtained through a structured interview.

RESULTS: In total, 302 migraineurs with a mean (±SD) age of 35.5 (±12.6) years were included. Patients who reported seasonal variation of migraine (n = 90; 29.8%) also reported more often interictal photophobia than the others (61/90, 67.8% vs 92/212, 43.4%, P < .0001). Patients reported sunlight or other bright light to trigger migraine attacks in 74.4% with seasonal migraine (SM) compared with 40.6% in patients with non-seasonal migraine (NSM) (P < .0001), but there were similar frequencies of attacks reported to be triggered by sleep, menstruation, and other precipitating factors. After adjusting for migraine with aura, migraine disability, chronic migraine, interictal photophobia, and insomnia, sunlight or other bright light, photophobia was still associated with SM (OR; 3.47, CI [95%]; 1.83-6.59, P < .0001).

CONCLUSIONS: Migraineurs in a subarctic area reporting seasonal variation of attack frequency also report increased interictal photophobia independent of other clinical factors. Chronobiological mechanisms and/or increased activity in the visual system may be responsible for this phenomenon.