title: Sleep assessment in a population-based study of chronic fatigue syndrome.
abstract: BACKGROUND
  Chronic fatigue syndrome (CFS) is a disabling condition that affects approximately 800,000 adult Americans. The pathophysiology remains unknown and there are no diagnostic markers or characteristic physical signs or laboratory abnormalities. Most CFS patients complain of unrefreshing sleep and many of the postulated etiologies of CFS affect sleep. Conversely, many sleep disorders present similarly to CFS. Few studies characterizing sleep in unselected CFS subjects have been published and none have been performed in cases identified from population-based studies.
  
  
  METHODS
  The study included 339 subjects (mean age 45.8 years, 77% female, 94.1% white) identified through telephone screen in a previously described population-based study of CFS in Wichita, Kansas. They completed questionnaires to assess fatigue and wellness and 2 self-administered sleep questionnaires. Scores for five of the six sleep factors (insomnia/hypersomnia, non-restorative sleep, excessive daytime somnolence, sleep apnea, and restlessness) in the Centre for Sleep and Chronobiology's Sleep Assessment Questionnaire (SAQ) were dichotomized based on threshold. The Epworth Sleepiness Scale score was used as a continuous variable.
  
  
  RESULTS
  81.4% of subjects had an abnormality in at least one SAQ sleep factor. Subjects with sleep factor abnormalities had significantly lower wellness scores but statistically unchanged fatigue severity scores compared to those without SAQ abnormality. CFS subjects had significantly increased risk of abnormal scores in the non-restorative (adjusted odds ratio [OR] = 28.1; 95% confidence interval [CI]= 7.4-107.0) and restlessness (OR = 16.0; 95% CI = 4.2-61.6) SAQ factors compared to non-fatigued, but not for factors of sleep apnea or excessive daytime somnolence. This is consistent with studies finding that, while fatigued, CFS subjects are not sleepy. A strong correlation (0.78) of Epworth score was found only for the excessive daytime somnolence factor.
  
  
  CONCLUSIONS
  SAQ factors describe sleep abnormalities associated with CFS and provide more information than the Epworth score. Validation of these promising results will require formal polysomnographic sleep studies.
authors.affiliation: Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. eru0@cdc.gov
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Unger
authors.forename: Rosane
authors.initials: R
authors.lastname: Nisenbaum
authors.forename: Harvey
authors.initials: H
authors.lastname: Moldofsky
authors.forename: Angela
authors.initials: A
authors.lastname: Cesta
authors.forename: Christopher
authors.initials: C
authors.lastname: Sammut
authors.forename: Michele
authors.initials: M
authors.lastname: Reyes
authors.forename: William C
authors.initials: WC
authors.lastname: Reeves
mesh_terms: D000328:Adult; D015897:Comorbidity; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis / Q000453:epidemiology; D005221:Fatigue / Q000175:diagnosis / Q000453:epidemiology; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007615:Kansas / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011237:Predictive Value of Tests; D015995:Prevalence; D018570:Risk Assessment; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000175:diagnosis / Q000453:epidemiology; D011795:Surveys and Questionnaires