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Sleep assessment in a population-based study of chronic fatigue syndrome.

Unger ER, Nisenbaum R, Moldofsky H, Cesta A, Sammut C, Reyes M, Reeves WC.
Sleep assessment in a population-based study of chronic fatigue syndrome.
BMC Neurology 4:6, 2004. (The complete electronic version of this article is available at http://www.biomedcentral.com/1471-2377/4/6)

Summary

Unrefreshing sleep is one of the most commonly reported symptoms among CFS patients, but few investigators have looked at sleep in detail and no study has measured characteristics of sleep in CFS patients identified from the general community. As part of the Wichita Longitudinal Surveillance Study, 339 subjects completed two questionnaires: the Centre for Sleep and Chronobiology's Sleep Assessment Questionnaire © (SAQ ©), which screens for non-restorative sleep, sleep apnea, restless legs syndrome, insomnia, and excessive daytime somnolence; and the Epworth Sleepiness Scale. Compared with subjects who had never been fatigued, CFS subjects were 28 times more likely to suffer from non-restorative sleep and 16 times more likely to have restless legs syndrome. Scores on the SAQ © excessive daytime somnolence scale or the Epworth scale were similar for CFS and never-fatigued subjects, which is consistent with studies finding that while fatigued, CFS subjects are not sleepy. These findings should be validated against polysomnographic sleep studies.

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.

Page last modified on May 8, 2006

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