Among studies that used ICHD criteria, prevalence estimates vary widely—from 2.4% to 27.5% in some American and European studies. The pain is generally made worse by physical activity. Migraines are believed to be due to a mixture of environmental and genetic factors. It is, however, believed to be a neurovascular disorder.
Note10-15 The prevalence in the present study is below estimates based on results of three population surveys in the United States: 22.7% in the National Health and Nutrition Examination Survey; 16.6% in the National Health Interview Survey; and 11.7% in the American Migraine Prevalence and Prevention study.