Self-report of headache in children and adolescents in Germany: possibilities and confines of questionnaire data for headache classification.

The aim of this study was to estimate prevalence rates of different types of primary headache in 9- to 14-year-old children in a population-based sample. Case definition was based on International Classification of Headache Disorders (ICHD) criteria. The possibility of implementing these criteria within a questionnaire format, which has been regarded as problematic by some authors, was the main focus of the study. A questionnaire was sent to children and adolescents in 6400 randomly drawn families in southern Lower Saxony. Valid questionnaires were returned by 61.1% of the sample. The overall prevalence rate for tension-type headache (TTH) (criteria C and D) was 17.6% and for migraine (criteria B, C and D) 13.1%. Despite the use of abridged criteria for headache classification, 35.5% of all children reported headache that could not be classified using the ICHD criteria. The response behaviour of these children indicated that they had difficulties reporting symptoms that were defining for migraine or TTH. The classifiability of headache does not seem to be dependent on age or frequency of headache, but rather on the number of 'I don't know' answers given regarding headache characteristics. It is likely that studies reporting prevalence rates that are limited to migraine and or TTH diagnoses underestimate the true prevalence of headache in children and adolescents.