Two year follow-up of sleep diaries and polysomnography in chronic fatigue syndrome: a cohort study

Background: Chronic fatigue syndrome (CFS) is a prevalent and debilitating symptom complex of unknown aetiology. Up to 96.8% of people with CFS report unrefreshing sleep and many describe, in qualitative interviews, changes in sleep over the course of their illness. Purpose: To establish whether subjective and objective sleep parameters change over a two-year follow-up period in patients with CFS. Methods: Twenty-two participants with CFS were recruited during routine consultations at a clinic in the North-East of England. All had their sleep characterised in a previously published cross-sectional study. Two were excluded from this analysis because they fulfilled criteria for a primary sleep disorder. The remaining 20 were contacted and 15 repeated fatigue- and sleep-quality questionnaires and sleep diaries, two years after their sleep was first characterised. Seven participants also repeated two consecutive nights of polysomnography. Paired statistical tests were used to compare follow-up with baseline measures. Results: Subjective questionnaires and sleep dairies did not show differences over two years follow-up. However, polysomnography demonstrated a higher proportion of stage one sleep (P < .01) and more awakenings per hour (P = .04) at follow-up. Conclusions: This study is the first to longitudinally assess sleep parameters in people with CFS. The results suggest that subjective perceptions of sleep remain stable, although objective measures indicated a tendency towards increased periods of lighter sleep. However, the small number of participants increases the likelihood that observed differences are Type I errors.