Evidence of a genetic factor in migraine with aura: A population-based Danish twin study

We studied the genetic influence on cause of migraine with aura (MA) by ana lyzing a twin population. The twin sample consisted of 2,026 monozygotic (M Z) twins and 3,334 same-sex dizygotic (DZ) twins, born from 1953 to 1960, f rom the population-based New Danish Twin Register. A validated questionnair e was used to screen for migraine, the response rate being 87%, and similar among MZ and DZ twins. All twin pairs with at least 1 twin with possible M A were interviewed by a physician experienced in headache diagnoses. The an swers from the questionnaire as well as the zygosity of the twins were blin ded for the interviewer. A total of 211 twin pairs were identified, of whom 77 pairs were MZ and 134 pairs were DZ. The lifetime prevalence of MA was 7% and with a male-to-female ratio of 1:1.1, The pairwise concordance rates were significantly higher in MZ (34%) than in DZ twin pairs (12%), emphasi zing the importance of genetic factors in MA. However, environmental factor s are also important, as the pairwise concordance rate was less than 100% i n MZ twin pairs. The recurrence risk of MA was 50% in MZ and 21% in DZ twin pairs. In nontwin siblings, the recurrence risk of IMA is 27%, which is si milar to the recurrence risk in DZ twins. This indicates that MA is not dev eloped due to specific environmental factors shared by the twins.