The prevalence of primary headache disorders in Nepal: a nationwide population-based study.

backgroundHeadache disorders are among the most prevalent and burdensome global public-health problems. Within countries, health policy depends upon knowledge of health within the local populations, but the South-East Asia Region (SEAR), among WHO's six world regions, is the only one for which no national headache prevalence data are available.

methodsIn a cross-sectional population-based study, adults representative of the Nepali-speaking population aged 18-65 years and living in Nepal were randomly recruited using stratified multistage cluster sampling. They were visited unannounced at home by trained interviewers who used a culturally-adapted Nepali translation of the structured Headache-Attributed Restriction, Disability, Social Handicap and Impaired Participation (HARDSHIP) questionnaire.

resultsThere were 2,100 participants (1,239 females [59.0 %], 861 males [41.0 %]; mean age 36.4 ± 12.8 years) with 9 refusals (participation rate 99.6 %). Over half (1,100; 52.4 %) were resident above 1,000 m and almost one quarter (470; 22.4 %) lived at or above 2,000 m. The 1-year prevalence of any headache was 85.4 ± 1.5 % (gender- and age-adjusted 84.9 %), of migraine 34.7 ± 2.0 % (34.1 %), of tension-type headache (TTH) 41.1 ± 2.1 % (41.5 %), of headache on ≥15 days/month 7.7 ± 1.1 % (7.4 %) and of probable medication-overuse headache (pMOH) 2.2 ± 0.63 % (2.1 %). There was a strong association between migraine and living at altitude ≥1,000 m (AOR = 1.6 [95 % CI: 1.3-2.0]; p < 0.001). There was a less strong association between TTH and urban dwelling (AOR = 1.3 [95 % CI: 1.1-1.6]; p = 0.003), and a possibly artefactual negative association between TTH and living above 1,000 m (AOR = 0.7 [95 % CI: 0.6-0.8]; p < 0.001).

conclusionHeadache disorders are very common in Nepal. Migraine is unusually so, and strongly associated with living at altitude, which in very large part accounts for the high national prevalence: the age- and gender- standardised prevalence in the low-lying Terai is 27.9 %. Headache occurring on ≥15 days/month is also common. This new evidence will inform national health policy and provide a basis for health-care needs assessment. However, research is needed to explain the association between migraine and altitude, since it may be relevant to health-care interventions.