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Epidemiologic Clues and the Classification of Primary Headaches

The paper by Göbel et al. in this issue of Cephalalgia extends recent studies of headache epidemiology (1-4) that have employed the International Headache Society (IHS) criteria to include Germany. While the authors report life-time prevalence in contrast to the one-year prevalence reported previously, their study offers an important clue to the validity of the IHS criteria for migraine versus tension-type headache. Clinicians and researchers have struggled to understand clearly the distinction between episodic tension-type headache and migraine. While it is widely accepted that these are different primary headache disorders, developing operational diagnostic criteria for each is not so straightforward. Central to this distinction are headache sufferers who meet all but one of the four criteria (number of attacks, duration of attacks, quality of pain, and associated symptoms) for migraine (defined by IHS 1.7 for migraine headache), a group sometimes referred to as 'migraine minus one'. This group accounts for 30 to 40% of apparent migraine sufferers and is highly heterogeneous. Evidence from the study of Göbel et al. suggests that a majority of the migraine minus one cases actually may be tension-type headache sufferers.