Bright light may trigger more attacks in migraine sufferers, particularly those whose headaches are accompanied by aura, according to research presented at the American Academy of Neurologys 57th annual meeting last month.

Researchers interviewed 169 female migraine sufferers in Norway98 experienced aura, while 71 did notand gave them questionnaires about their headaches. There were no differences between the two groups in sleep cycles, sleep disturbances or shift work that would affect their sleep schedules.

Exposure to intense light could lead to attacks for 86% of women with aura vs. 59% of those without aura, the study found. Also, 62% of the women with aura became extremely sensitive to light during and between attacks vs. 41% of those without aura.

This supports the theory that, in people who experience migraines, the neurons in the occipital lobe of the brainwhich is the part that is the primary site for visionare hyperexcitable, or easier to trigger, says Karl Alstadhaug, M.D., the neurologist from Bodo, Norway, who presented the study results.

Some other findings: Nearly half (47%) of those with aura had more frequent attacks during the brighter summer season than during the winter, compared to 17% of those without aura. And, those with aura were also more likely to wear sunglasses to prevent attacks.