Abstract
BACKGROUND: Recent studies indicate that migraine affects 14-15% of the global population, tension-type headache (TTH) around 26%, and medication-overuse headache (MOH) 1-2%. While these estimates highlight the impact of these conditions on population health, their reliability is compromised by the variable quality of contributing studies. In response, the Global Campaign against Headache has supported epidemiological studies in all parts of the world, using standardized methods. METHODS: We conducted a meta-analysis of individual participant data from these studies, accepting only population-representative data (17 countries from all world regions). All included studies were cross-sectional surveys of adults aged 18-65 years using the Headache-Attributed Restriction, Disability, Social Handicap and Impaired Participation (HARDSHIP) questionnaire. Algorithmic diagnosis applying modified International Classification of Headache Disorders (ICHD) criteria identified the headache disorders of public-health importance: migraine, TTH and probable MOH (pMOH: the association of headache on ≥ 15 days/month [H15+] and reported medication overuse). Two sets of estimates were made for migraine and TTH, one excluding those with H15+ (standard process), the other including these (extended process). We analysed associations with demographical variables, and, accordingly, adjusted prevalence estimates for age, gender and country income level. RESULTS: We included 41,614 individuals, with over-representations of females (22,278 [53.5%]) and of participants from lower-middle income countries (59.7%; global 37.8%). Age-distribution was similar to that of the world. Overall, 65.5% (95% CI: 65.0-66.0) reported headache during the previous year, females (72.1% [71.5-72.7]) more than males (57.9% [57.2-58.6]). Migraine was more common among females (standard process: 29.5% [28.9-30.1]; extended process: 33.1% [32.5-33.7]) than males (18.6% [18.1-19.2]; 20.1% [19.6-20.7]), as was pMOH (5.6% [5.3-5.9] vs. 2.3% [2.1-2.5]). TTH was similarly prevalent among males (33.4% [32.8-34.1]; 34.9% [34.2-35.5]) and females (31.2% [30.6-31.8]; 33.2% [32.6-33.8]). Headache was more prevalent in high/upper-middle income countries (71.4% [70.6-72.2]) than in low/lower-middle income (63.0% [62.5-63.6]). Prevalence estimates adjusted for age, gender and income level were 65.0% (64.6-65.5) for any headache, 23.5% (23.1-23.9; standard process) and 25.9% (25.4-26.3; extended process) for migraine, 33.2% (32.7-33.6) and 34.7% (34.3-35.2) for TTH, and 4.1% (3.9-4.3) for pMOH. CONCLUSIONS: About 65% of the world's population aged 18-65, likely to include most of the world's workforce, will have headache during the coming year, about 25% migraine and 4% pMOH. Both these estimates are higher than previous comparable estimates, and we believe them to be the best currently available for this population. Our estimate of TTH prevalence (about 33%) is probably substantially too low, since methodological constraints precluded identification of TTH in those with concomitant migraine.