Chronic migraine prevalence, disability, and sociodemographic factors: results from the American Migraine Prevalence and Prevention Study.

OBJECTIVES To estimate the prevalence and distribution of chronic migraine (CM) in the US population and compare the age- and sex-specific profiles of headache-related disability in persons with CM and episodic migraine. BACKGROUND Global estimates of CM prevalence using various definitions typically range from 1.4% to 2.2%, but the influence of sociodemographic factors has not been completely characterized. METHODS The American Migraine Prevalence and Prevention Study mailed surveys to a sample of 120,000 US households selected to represent the US population. Data on headache frequency, symptoms, sociodemographics, and headache-related disability (using the Migraine Disability Assessment Scale) were obtained. Modified Silberstein-Lipton criteria were used to classify CM (meeting International Classification of Headache Disorders, second edition, criteria for migraine with a headache frequency of ≥15 days over the preceding 3 months). RESULTS Surveys were returned by 162,756 individuals aged ≥12 years; 19,189 individuals (11.79%) met International Classification of Headache Disorders, second edition, criteria for migraine (17.27% of females; 5.72% of males), and 0.91% met criteria for CM (1.29% of females; 0.48% of males). Relative to 12 to 17 year olds, the age- and sex-specific prevalence for CM peaked in the 40s at 1.89% (prevalence ratio 4.57; 95% confidence interval 3.13-6.67) for females and 0.79% (prevalence ratio 3.35; 95% confidence interval 1.99-5.63) for males. In univariate and adjusted models, CM prevalence was inversely related to annual household income. Lower income groups had higher rates of CM. Individuals with CM had greater headache-related disability than those with episodic migraine and were more likely to be in the highest Migraine Disability Assessment Scale grade (37.96% vs. 9.50%, respectively). Headache-related disability was highest among females with CM compared with males. CM represented 7.68% of migraine cases overall, and the proportion generally increased with age. CONCLUSIONS In the US population, the prevalence of CM was nearly 1%. In adjusted models, CM prevalence was highest among females, in mid-life, and in households with the lowest annual income. Severe headache-related disability was more common among persons with CM and most common among females with CM.