Epidemiology of chronic daily headache in the general population

Background and Objectives,-Although chronic daily headache, mainly transfor med migraine, is an important reason for consultation in headache clinics, its actual prevalence is unknown, This study analyzes the prevalence of the different types of chronic daily headache in an unselected population, Methods,-A questionnaire exploring headache frequency was distributed to 22 52 unselected subjects. Those having headache 10 or more;gaps per month wer e given a headache diary and were seen by a neurologist who classified thei r headaches. The varieties of chronic daily headache were classified accord ing to the second revision of IHS criteria proposed by Silberstein et al pu blished in Neurology 1996;47:871. Results,-The questionnaire was returned by 1883 subjects (83.5%), One hundr ed thirty-five admitted to headache 10 or more days per month. Chronic dail y headache criteria were fulfilled by 89 individuals (4.7%). Eighty were wo men, Forty-two (47.2% of subjects with chronic daily headache and 2.2% of a ll subjects) had chronic tension-type headache. Analgesic overuse was found in 8 (17%),Transformed migraine was diagnosed in 45 (50.6% of subjects wit h chronic daily headache and 2.4% of all subjects),'Fourteen (31.1%) indivi duals with this form of chronic daily headache overused ergots or analgesic s, The remaining 2 cases in this series met the criteria of new daily persi stent headache, No one was diagnosed as having hemicrania continua, Conclusions,-Almost 5% of the general population (9% of women) suffers from chronic daily headache, the proportion of chronic tension-type headache an d transformed migraine being quite similar Less than one third overuse anal gesics; The prevalence of chronic daily headache subtypes shown here differ s from data obtained from headache clinics, emphasizing that caution is nee ded in extrapolating data from specialized units to the general population.