Over 600 million people aged 18–65 will have headache tomorrow: global 1-day prevalence and recall bias from a meta-analysis of individual participant data (N = 38,512) from the general populations of 15 countries

Abstract Background Our recent estimate of the global 1-year prevalence of headache among those aged 18–65 years was 65%: considerably higher than previous estimates, but based solely on high-quality epidemiological data derived from a large population-based sample. Here we present complementary estimates of 1-day prevalence. Methods We performed a meta-analysis of individual participant data from cross-sectional surveys among population-representative samples (age range 18–65 years) from 15 countries and all world regions. All used the Headache-Attributed Restriction, Disability, Social Handicap and Impaired Participation (HARDSHIP) questionnaire, including the question “did you have a headache yesterday?”, from which 1-day prevalence was determined. An algorithmic process applying modified ICHD criteria yielded separate estimates for migraine, tension-type headache (TTH) and probable medication-overuse headache (pMOH: the association of headache on ≥ 15 days/month and medication overuse). We analysed associations with age, gender and country-income level, and adjusted prevalence estimates for these factors. We calculated predicted 1-day prevalence from 1-year prevalence and reported headache frequency. Results Among the 38,512 participants, females (53.4%) and participants from low- (17.1%) or lower-middle-income countries (64.6%) were overrepresented, but age distribution fairly matched that of the world. Overall, 13.7% (95% CI: 13.3–14.0) reported headache yesterday, females (17.1% 16.6–17.6) more than males (9.7% 9.3–10.2). Migraine was the most common headache type yesterday (6.0% 5.8–6.3), followed by TTH (4.1% 3.9–4.3) and pMOH (2.3% 2.2–2.5). One-day headache prevalence was higher in low/lower-middle-income countries (13.9% 13.6–14.3) than in high/upper-middle-income countries (12.4% 11.6–13.2). Predicted 1-day prevalence (10.9% 10.7–11.1) was considerably lower than observed 1-day prevalence (13.7% 13.3–14.0), although not among those with pMOH (3.1% 3.0-3.3 versus 2.3% 2.2–2.5). Adjusted for age, gender and country-income level, global 1-day prevalence estimates were 13.1% (12.8–13.5) for any headache, 5.7% (5.5–5.9) for migraine, 3.9% (3.7–4.1) for TTH and 2.4% (2.3–2.6) for pMOH, with 1.0% undiagnosed. Conclusion Assuming yesterday was no different from any other day, an estimated 13.1% ( N = 641,900,000) of the world’s population aged 18–65 years will have headache tomorrow; almost half will be migraine. People with migraine or TTH underestimate the frequency of headache episodes. Since headache-attributed burden is usually estimated from recalled frequency over 1–12 months, this also may be underestimated.