Subjective sleep quality and daytime sleepiness in a large sample of patients with chronic fatigue syndrome (CFS)

Chronic fatigue syndrome (CFS) is characterised by incapacitating fatigue in combination with a number of minor criteria, including unrefreshing sleep without further specifications, in the absence of psychiatric and internal disease. As little data exist on subjective sleep quality and daytime sleepiness, these parameters were assessed in a large sample of CFS patients. Consecutive patients with a diagnosis of CFS in a tertiary referral centre filled out the Fatigue Questionnaire (FQ), Medical Outcomes Study 36-Item Short Form Health Survey (MOS SF-36), Epworth Sleepiness Scale (ESS) and Pittsburgh Sleep Quality Index (PSQI). Inclusion comprised 415 individuals (mean age 40.5 yr, SD 7.9, range 18-64; 86% female). Mean FQ (26.90; SD 4.04), mean Global Physical Health from the MOS SF-36 (29.30; SD 12.25) and Global Mental Health from the MOS SF-36 (49.62; SD 18.31) scores corresponded with literature data for similar CFS samples. High mean ESS (10.51; SD 5.52) and global PSQI (10.17; SD 4.02) were observed. No significant relationship was found between ESS and global PSQI. In contrast, regression analysis demonstrated a significant cubic relation between ESS and 'PSQI without daytime dysfunction: A subgroup (n = 69) with an insomnia-like phenotype low ESS (< 5), high PSQI (mean 11.51; SD 3.86) was observed. The assessment of subjective sleep quality and daytime sleepiness in a large sample of CFS patients indicated high mean PSQI and ESS values. ESS and 'PSQI without daytime dysfunction' were inversely related at the spectral ends of ESS. A distinct subgroup with clinical features of insomnia was identified.

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