Abstract
OBJECTIVE: To investigate familial occurrence of migraine with and without aura. DESIGN: Familial occurrence of migraine with and without aura among first degree relatives and spouses of probands with migraine with or without aura and those who had never had migraine. All interviews of first degree relatives and spouses were done blindly by a neurological resident. The operational diagnostic criteria of the International Headache Society were used. SETTING: General population from Copenhagen County. SUBJECTS: The 378 probands had 1109 first degree relatives and 229 spouses. MAIN OUTCOME MEASURES: Patterns of familial aggregation of migraine with and without aura as assessed by calculation of the population relative risk. RESULTS: Compared with the general population the first degree relatives of probands with migraine without aura had 1.9 times the risk of migraine without aura and 1.4 times the risk of migraine with aura. The first degree relatives of probands with migraine with aura had nearly four times the risk of migraine with aura and no increased risk of migraine without aura. The first degree relatives of probands who had never had migraine had no increased risk of migraine either with or without aura. Spouses of probands with migraine without aura had 1.4 times the risk of migraine without aura whereas spouses of probands with migraine with aura had no increased risk of migraine with aura. CONCLUSION: The different familial patterns indicate that migraine without aura and migraine with aura have a different aetiology. Migraine without aura seems to be caused by a combination of genetic and environmental factors whereas migraine with aura is probably determined largely or exclusively by genetic factors.