Epidemiology of chronic fatigue syndrome.

Background: Chronic fatigue syndrome (CFS) is a controversial disorder with different case definitions, aetiological models and proposed treatments. An epidemiological approach is likely to bring some clarity to the field.

Aim: The aim of this article is to review the literature on the epidemiology of fatigue, chronic fatigue and CFS.

Method: A literature search was conducted using the databases Medline and Pubmed as well as the reference lists of recent reviews to identify the relevant studies. The aim was not to do a systematic review but to review the key studies in the area to highlight the methodological issues.

Results: The review is organized according to the following areas: the prevalence of fatigue and chronic fatigue, the prevalence and incidence of CFS, epidemiological associations such as gender, social class and psychiatric co-morbidity and CFS in special groups such as those recovering from a viral infection, specific occupational groups and Gulf War veterans.

Conclusion: While fatigue as a symptom is very common, CFS is relatively rare. Many of the epidemiological associations seen in specialist clinics are not found in community samples. It is unlikely that one specific causal factor can explain CFS. Future studies should go beyond estimating the prevalence to testing more complex aetiological models.