FAMILIAL RISK OF MIGRAINE - A POPULATION-BASED STUDY

Estimates of familiar aggregation of migraine have varied considerably due, in part, to methodological differences among studies. We conclud ed a population-based study of 73 clinically confirmed probands with m igraine, 72 matched control probands, and 511 of their first-degree re latives, all of whom were directly interviewed. The risk of migraine w as 50% more likely in relatives of migraine probands than in relatives of controls, Migraine risk was considerably higher among relatives of probands with disabling migraine compared with relatives of probands with minimal disability. Moreover, for probands with minimal disabilit y, no excess risk of migraine in female relatives was observed. Finall y, in relatives of male migraine probands, there appears to be an exce ss risk of migraine with aura. A borderline significant relative risk of 4.04 was observed. No excess risk was observed among relatives of m ale probands who had migraine without aura. This study suggests that f amilial factors (environment related to the family or genetic factors) account for less than one-half of all migraine cases in the populatio n. Degree of disability in the proband appears to influence familial r isk These results suggest that the development of migraine is determin ed by complex genetic as well as environmental factors.