Chronic Migraine Epidemiology and Outcomes – International (CaMEO-I) Study: methods and global findings for diagnosis rates and care

Abstract text (incl. figure legends and references)

Objective: To describe the methodology and present findings on migraine diagnosis, consulting, and current medication use for migraine across 6 countries.

Methods: CaMEO-I was a cross-sectional, observational, web-based study in 2021 in 6 countries: US, Canada, UK, Germany, France, and Japan. A validated questionnaire identified patients with migraine based on modified International Classification of Headache Disorders, 3rd ed (mICHD-3) criteria. Qualified respondents provided sociodemographic background, headache features, migraine disability based on the Migraine Disability Assessment Scale (MIDAS), and history of consulting, diagnosis, and treatment patterns.

Results: A total of 14,492 individuals met criteria for migraine (approximately 2400 from each country) and were included in this analysis. The mean age among migraine respondents ranged from 40.3-42.3 years and the majority were female (68.7-73.8%). Median monthly headache days (MHDs) ranged from 2.3 to 3.3 days, with between 5.4% (France) to 9.5% (Japan) of respondents reporting ≥15 MHDs. Moderate-to-severe migraine-related disability was reported between 30.3% (Japan) to 52.0% (Germany) of migraine respondents (Figure). Self-reported medical diagnosis (SRMD) rates for migraine, chronic/transformed migraine, or menstrual migraine among those meeting the ICHD-3 case definition ranged from 42.8% (Japan) to 49.3% (US). The SRMD rates for chronic/transformed migraine ranged from 0.7% (Japan) to 4.8% (US) of respondents with migraine. In the overall migraine population, rates of current preventive use ranged from 6.4% (Japan) to 16.8% (US).

Conclusions: Between one-third and one-half of respondents who met mICHD-3 criteria for migraine reported moderate to severe migraine-related disability as measured by MIDAS. While there were between-country differences in the proportion of CaMEO-I respondents with an SRMD of migraine and chronic migraine, underdiagnosis of migraine was a concern in each country studied.