Prevalence Of Headache In Europe: A Review For The Eurolight Project

Literature search

A comprehensive literature search was performed to identify population-based studies of headache and migraine. Searches were performed with PubMed using the expressions “migraine epidemiology”, “headache epidemiology” and “migraine prevalence” or “headache prevalence” for each European country. References in relevant publications have also been examined. Only studies in English, German, French or Spanish were considered.

Data extraction

The information extracted was the country of origin, year of publication, population characteristics and the prevalence estimates for headache, migraine, tension-type headache (TTH) and chronic headache, both overall and for each gender, and for various age categories.

Case definitions

Only studies where the headache diagnoses are made according to the International Classification of Headache Disorders, first edition (ICHD-1) from 1988 [6] or according to ICHD-2 from 2004 [7] have been used. This classification has later been incorporated in the International Classification of Diseases (ICD-10) [8]. Hence, we have included epidemiologic studies that have appeared after 1988 on migraine (ICD-10 diagnosis G43) and TTH (G44.2), the two types that affect the great majority of headache patients. For migraine, we have not distinguished between migraine with (G43.1) and without (G43.0) aura. This differentiation can reliably be made only in studies using personal interview, preferably by a headache specialist. In addition, it is not known whether the two types differ markedly with regard to the patients’ suffering and subsequent economic consequences. For practical reasons, the diagnosis in most headache epidemiologic studies has been made according to somewhat modified criteria, and such studies have also been included.

In order to comprise all headache patients, we have also included epidemiologic studies that have investigated headache in general. The term “headache” is not, however, defined in the ICHD classifications, and we have therefore included studies on headache prevalence that appeared before 1988. For TTH, the term “chronic” has been applied to patients who have this type of headache for ≥15 days per month on average for ≥3 months (ICHD-1 and -2). In many headache studies, a similar definition has been given to patients with headache, irrespective of whether it is of the tension type or not. We have also gathered data on “chronic headache” (i.e. ≥15 days per month or “daily” headache) to assess the prevalence of these patients who are probably most incapacitated by their condition. A subgroup of these patients are overusing acute medication, a condition termed “Medication overuse headache” (MOH) in the IDHD-2. We have also collected data on this frequent and possibly preventable condition.

Source populations

For our purpose, we have included only studies performed on the whole population or a representative sample of the whole population within a certain age range in a community, town or country. We have accordingly not included studies based on selected populations (clinic based, in workplaces, among university students, etc.). Since the primary school is obligatory in all European countries, studies on headache in children and youth based on schools have been included.

Period prevalences

For many patients, headache is troublesome only in certain phases of life. For this reason, most headache epidemiological studies have asked the subjects on headache within a limited time span, usually the last year. The 1-year prevalence figure indicates the proportion of the population that has an active disease, which is more relevant than lifetime prevalence for health economic calculations. Data on lifetime prevalence are also considered less reliable due to recall problems, at least in the elderly. In children and adolescents, one may assume that the lifetime and 1-year prevalences are not very different. The studies with 3-month or not specified timeframe has also been included since these time frames will also give a fairly accurate estimate of the proportion of the population with headache in the relatively recent past, usually not very different from the 1-year prevalence.