The prevalence and demographic associations of headache in the adult population of Peru: a national cross-sectional population-based study

Background The Global Campaign against Headache is conducting a series of population-based studies to fill the large geographical gaps in knowledge of headache prevalence and attributable burden. One major region not until now included is South America. Here we present a study from Peru, a country of 32.4 million inhabitants located at the west coast of South America, notable for its high Andes mountains. Methods The study was conducted in accordance with the standardized methodology used by the Global Campaign. It was a cross-sectional survey using cluster randomised sampling in five regions to derive a nationally representative sample, visiting households unannounced, and interviewing one randomly selected adult member (aged 18-65 years) of each using the Headache-Attributed Restriction, Disability, Social Handicap and Impaired Participation (HARDSHIP) questionnaire translated into South American Spanish. The neutral screening question ("Have you had headache in the last year?") was followed by diagnostic questions based on ICHD-3 and demographic enquiry. Results The study included 2,149 participants from 2,385 eligible households (participating proportion 90.1%): 1,065 males and 1,084 females, mean age 42.0 +/- 13.7 years. The observed 1-year prevalence of all headache was 64.6% [95% CI: 62.5-66.6], with age-, gender- and habitation-adjusted prevalences of 22.8% [21.0-24.6] for migraine (definite + probable), 38.9% [36.8-41.0] for tension-type headache (TTH: also definite + probable), 1.2% [0.8-1.8] for probable medication-overuse headache (pMOH) and 2.7% [2.1-3.5] for other headache on >= 15 days/month (H15+). One-day prevalence of headache (reported headache yesterday) was 12.1%. Migraine was almost twice as prevalent among females (28.2%) as males (16.4%; aOR = 2.1; p < 0.001), and strongly associated with living at very high altitude (aOR = 2.5 for > 3,500 versus < 350 m). Conclusion The Global Campaign's first population-based study in South America found headache disorders to be common in Peru, with prevalence estimates for both migraine and TTH substantially exceeding global estimates. H15 + was also common, but with fewer than one third of cases diagnosed as pMOH. The association between migraine and altitude was confirmed, and found to be strengthened at very high altitude. This association demands further study.