Prevalence of chronic migraine and medication overuse headache in Germany--the German DMKG headache study.

Population-based epidemiological studies about the prevalence of chronic migraine using the 2004 International Headache Society (IHS) classification definition are rare. We analysed the data of the Deutsche Migräne und Kopfschmerz Gesellschaft headache study, which included 7417 adults in three regions of Germany, with respect to their headache. Additionally, body mass index, alcohol consumption and smoking behaviour were recorded. Using the IHS definition from 2004, chronic migraine was diagnosed in 0.2% of the population. Half of these patients also fulfilled the criteria of medication overuse headache (MOH). The distribution of migraine attacks per subject was highly skewed, with only 14% of all migraine patients having more than six migraine attacks per month. Patients with chronic migraine or MOH seem more often to be active smokers than controls without headache. A body mass index of ≥ 30 was present significantly more often in patients with MOH than in controls or in patients with episodic migraine. The skewed distribution of the numbers of attacks per patient supports the recommendation to differentiate between episodic migraine with low and high attack frequency, as is done in the classification of tension-type headache. It further suggests that migraine with high attack frequency might be biologically different. The higher prevalence of smokers and of patients with a body mass index ≥ 30 in chronic migraine or MOH supports the idea of a frontal dysfunction in these patients.