A Comparison of the Chronic Migraine Epidemiology and Outcomes (CaMEO) Study and American Migraine Prevalence and Prevention (AMPP) Study: Demographics and Headache-Related Disability.

OBJECTIVE: To compare the methods and baseline characteristics of the American Migraine Prevalence and Prevention (AMPP) and Chronic Migraine Epidemiology and Outcomes (CaMEO) studies.

BACKGROUND: The AMPP and CaMEO studies are the largest longitudinal efforts designed to improve our understanding of episodic and chronic migraine in the United States. The studies have complementary strengths and weaknesses.

METHODS: This analysis compares and contrasts the study methods and participation rates of the AMPP and CaMEO studies. We then compare and contrast baseline results in terms of demographic characteristics, headache features, and disability as measured by the Migraine Disability Assessment Scale (MIDAS) among people with episodic and chronic migraine.

RESULTS: AMPP and CaMEO sampled from panels constructed to be representative of the US population. The AMPP Study collected data using a mailed questionnaire while CaMEO relied on a web survey methodology. Response rates were higher in AMPP (64.8%) than in CaMEO (16.5%). Both studies assessed headache features using the American Migraine Study/AMPP diagnostic module. Both identified persons with episodic (<15 headache days/month) and chronic migraine (≥15 headache days/month) based on the International Classification of Headache Disorders. AMPP collected data annually over 5 years, while CaMEO collected data quarterly over 15 months. Baseline demographic distribution was generally similar, indicating that each study was broadly representative of the US population. The proportion of persons with migraine who had chronic migraine was similar (AMPP, 6.6%; CaMEO, 8.8%). Respondents had similar median headache frequency (days/month) by sex for chronic migraine (AMPP: men = 21.7, women = 20.0; CaMEO: men = 20.0, women = 20.0) and episodic migraine (AMPP: men = 1.7, women = 2.0; CaMEO: men = 2.0, women = 3.0). Median MIDAS scores were substantially higher in both studies for chronic migraine (severe disability [Grade IV]; AMPP: men = 33.0, women = 45.0; CaMEO: men = 32.0, women = 38.0) than episodic migraine (little/mild disability [Grade I/II]; AMPP: men = 3.0, women = 6.0; CaMEO: men = 4.0, women = 7.0). Rates of moderate/severe disability (Grade III/IV) were substantially higher in both studies for chronic migraine (AMPP: men = 66.9%, women = 78.9%; CaMEO: men = 71.0%, women = 82.6%) than episodic migraine (AMPP: men = 23.0%, women = 31.8%; CaMEO: men = 26.7%, women = 37.9%). More women than men respondents in both studies experienced moderate/severe disability.

CONCLUSIONS: AMPP and CaMEO are longitudinal cohort studies that used different methods, but yielded similar results for demographic features, headache frequency, and headache-related disability. Both studies found more severe headache-related disability in those with chronic versus episodic migraine.