Epidemiology of migraine

One-year migraine prevalence rates in the general population for Western countries vary from 4% to 9% in men and from 11% to 25% in women. Non-Western countries report lower figures. Incidence rates for people under 30 years of age vary from 1.5 to 6 per 1000 person-years in men and from 3 to 24 per 1000 person-years in women. Data on the prevalence of migraine in general, on the gender ratio and on the variations in prevalence in the different age ranges are fairly comparable and can be regarded as very close to reality. On the contrary, data on the incidence of migraine, on the prevalence of different migraine subtypes, such as migraine with aura and the so-called migrainous disorder, and on the frequency of migraine attacks show a striking discordance that somewhat undermines their reliability. The main critical points in prevalence and incidence studies are migraine definition and the methodological approaches used for case screening. Even if International Headache Society (IHS) classification is certainly an improvement over previous tools used in epidemiological studies, the diagnostic criteria for migraine without aura are quite scanty and not easily remembered by subjects belonging to the general population, and those for migraine with aura appear not only difficult to translate for use in a questionnaire or an interview, but also too loose. In particular, the lack of any low-end limit for aura duration may cause an overestimation of migraine with aura prevalence.