A POPULATION-BASED INCIDENCE STUDY OF CHRONIC FATIGUE

Background. Most research on syndromes of chronic fatigue has been con ducted in clinical settings and is therefore subject to selection bias es. We report a population-based incidence study of chronic fatigue (C F) and chronic fatigue syndrome (CFS). Methods. Questionnaires assessi ng fatigue and emotional morbidity were sent to 695 adult men and wome n who had replied to a postal questionnaire survey 1 year earlier. Pos sible CFS cases, subjects with probable psychiatric disorder and norma l controls were interviewed. Results. Baseline fatigue score, the leve l of emotional morbidity and a physical attribution for fatigue were r isk factors for developing CF. However, after adjusting for confoundin g, premorbid fatigue score was the only significant predictor. A minor ity of CF subjects, all female, had consulted their general practition er; higher levels of both fatigue and emotional morbidity were associa ted with consultation. Possible CFS cases reported similar rates of cu rrent and past psychiatric disorder to psychiatric controls, but after controlling for fatigue or a diagnosis of neurasthenia the current ra tes were more similar to those of normal controls. Two new cases of CF S were confirmed. Conclusions. Both fatigue and emotional morbidity ar e integral components of chronic fatigue syndromes. The demographic an d psychiatric associations of CFS in clinical studies are at least par tly determined by selection biases. Given that triggering and perpetua ting factors may differ in CFS, studies that examine the similarities and differences between chronic fatigue syndromes and psychiatric diso rder should consider both the stage of the illness and the research se tting.