Prevalence of primary chronic headache in a population-based sample of 30- to 44-year-old persons. The Akershus study of chronic headache.

BACKGROUND: Prevalence data on primary chronic headache in the general population based on clinical interviews by physicians are lacking.

METHODS: In a cross-sectional epidemiological survey, a random sample of 30,000 persons from Akershus County, aged 30-44 years, were sent a postal questionnaire. Those with self-reported chronic headache within the last month and/or year were invited to a semi-structured diagnostic interview and a physical and neurological examination conducted by 2 neurological residents with experience in headache diagnostics. The diagnoses were made according to the International Classification of Headache Disorders, 2nd edition, 2004, and relevant revisions.

RESULTS: The questionnaire response rate was 71%, and the participation rate of the interview was 74%. The 1-year prevalence of primary chronic headache was 2.9%. Chronic tension-type headache (CTTH) and probable chronic tension-type headache (pCTTH) had 1-year prevalences of 1.6 and 1.2%, respectively. The prevalences of other primary chronic headaches were: chronic migraine (CM) 0.01%, probable CM 0.09% and other subtypes 0.04%. Co-occurrence of migraine was frequent, as 42% with CTTH and 55% with pCTTH had migraine.

CONCLUSION: Primary chronic headache is prevalent in the general population. The majority has CTTH or pCTTH, while CM and other primary chronic headaches are rare.