Improving quality in population surveys of headache prevalence, burden and cost: key methodological considerations

Population-based studies of headache disorders are important. They inform needs assessment and underpin service policy for a set of disorders that are a public-health priority. On the one hand, our knowledge of the global burden of headache is incomplete, with major geographical gaps; on the other, methodological differences and variable quality are notable among published studies of headache prevalence, burden and cost. The purpose here was to start the process of developing standardized and better methodology in these studies. An expert consensus group was assembled to identify the key methodological issues, and areas where studies might fail. Members had competence and practical experience in headache epidemiology or epidemiology in general, and were drawn from all WHO world regions. We reviewed the relevant literature, and supplemented the knowledge gathered from this exercise with experience gained from recent Global Campaign population-based studies, not all yet published. We extracted methodological themes and identified issues within them that were of key importance. We found wide variations in methodology. The themes within which methodological shortcomings had adverse impact on quality were the following: study design; selection and/or definition of population of interest; sampling and bias avoidance; sample size estimation; access to selected subjects (managing and reporting non-participation); case definition (including diagnosis and timeframe); case ascertainment (including diagnostic validation of questionnaires); burden estimation; reporting (methods and results). These are discussed.

The global burden of headache: a documentation of headache prevalence and disability worldwide

This study, which is a part of the initiative 'Lifting The Burden: The Global Campaign to Reduce the Burden of Headache Worldwide', assesses and presents all existing evidence of the world prevalence and burden of headache disorders. Population-based studies applying International Headache Society criteria for migraine and tension-type headache, and also studies on headache in general and 'chronic daily headache', have been included. Globally, the percentages of the adult population with an active headache disorder are 46% for headache in general, 11% for migraine, 42% for tension-type headache and 3% for chronic daily headache. Our calculations indicate that the disability attributable to tension-type headache is larger worldwide than that due to migraine. On the World Health Organization's ranking of causes of disability, this would bring headache disorders into the 10 most disabling conditions for the two genders, and into the five most disabling for women.

Prevalence of temporomandibular symptoms in a large United States metropolitan area

The prevalence of five symptoms of temporomandibular disorder and associated symptoms of pain, headache, and stress was estimated in a random telephone survey of a large United States metropolitan area. The prevalences for nocturnal bruxing, joint noise with use, soreness on waking, soreness with use, and diurnal clenching were roughly equivalent (ranging from 8% to 12%) and were within the range of prevalences reported in previous studies. Overall, 149 of the 500 respondents reported one or more of the five symptoms. Symptoms were not more prevalent among women than men, but were more prevalent among younger respondents. Soreness on waking and daytime clenching were the only symptoms significantly associated with report of pain. Pain was more commonly reported by respondents with multiple (four or five) symptoms. The results are compared with those of previous random surveys, and limitations to generalization of the present findings are discussed.