Headaches worldwide - one-year prevalences by region 2011

Missing figures indicate a lack of relevant studies, not the absence of the disorder in the specific region.
The source states that most of the information was collected in a questionnaire survey of neurologists, general practitioners and patients’ representatives from 101 countries, performed from October 2006 until March 2009. Epidemiological data were compiled from published studies through a systematic review, and supplemented by data gathered in population-based studies undertaken within the Global Campaign.
* Including headache, migraine, tension-type headache and medication-overuse headache from population-based studies by WHO region.
** The source states that thediscrepancy between 80 % for tension-type headache and 56.1 % for all headache in Europe arises because these are means of estimates from different studies.