Chronic Migraine Epidemiology and Outcomes – International (CaMEO-I) Study: Methods and multi-country baseline findings for diagnosis rates and care

Background: The Chronic Migraine Epidemiology and Outcomes-International study provides insight into people with migraine in multiple countries. Methods: This cross-sectional, observational, web-based cohort study was conducted in Canada, France, Germany, Japan, United Kingdom, and United States. An initial Screening Module survey solicited general healthcare information from a representative sample and identified participants with migraine based on modified International Classification of Headache Disorders-3 criteria; those with migraine completed a detailed survey based on validated migraine-specific assessments. Results: Among 90,613 people who correctly completed the screening surveys, 76,121 respondents did not meet the criteria for migraine, while 14,492 did. Among respondents with migraine, mean age ranged from 40 to 42 years. The median number of monthly headache days ranged from 2.33 to 3.33 across countries, while the proportion of respondents with moderate-to-severe disability (measured by Migraine Disability Assessment) ranged from 30% (Japan) to 52% (Germany). The proportion of respondents with ≥15 monthly headache days ranged from 5.4% (France) to 9.5% (Japan). Fewer than half of respondents with migraine in each country reported having received a migraine diagnosis. Conclusion: These results demonstrated high rates of migraine-related disability and underdiagnosis of migraine across six countries. This study will characterize country-level burden, treatment patterns, and geographical differences in care.