Clinical reviewSleep in the chronic fatigue syndrome
Introduction
Recurring complaints of disturbed sleep and fatigue are very common among the general population. Patients who present with a combination of these symptoms may perceive malfunction of sleep as the prime cause of tiredness and other impairments in daily life. Because of this attribution, dissatisfaction with daytime functioning may be an incentive to seek medical help for a presumed disturbance of sleep.
Fatigue is a common denominator referring to various aspects of impaired physical, mental, emotional and neurocognitive functioning. Lack of energy, weakness, attention deficits, memory problems and irritability are typically associated with the construct of fatigue. It is a frequent manifestation of a variety of medical, neurological and psychiatric diseases. It may also appear as a side effect of pharmacological treatment.
Presently, there is ample evidence to confirm that sleep curtailment, whether experimentally induced or self-imposed, is causally associated with fatigue. Likewise, primary sleep disorders (PSD) are a known cause of fatigue and excessive daytime sleepiness (EDS). Clinical improvement of these symptoms can be expected from adequate treatment of the underlying sleep disorder.
Finally, fatigue often remains unexplained, leading to the construct of chronic fatigue syndrome (CFS), in which unrefreshing sleep is a prominent (but ill-defined) feature.
The aim of the present review is to:
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give an overview of definitions, health impact and epidemiology of CFS;
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explore current insights into restorative and nonrestorative aspects of sleep;
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assess the relations between sleep and CFS.
Section snippets
Definitions, health impact and epidemiology of CFS
CFS is characterized by long lasting pathologic fatigue with a disabling impact on professional, social and daily functioning. The absence of any obvious underlying disease, and the presence of a number of associated clinical features are fundamental to this disorder. The term CFS was coined in 1988 by Holmes et al. in a publication of the US Centers for Disease Control and Prevention (CDC).1 Since then, several new case definitions have been introduced. In 1994, revised CDC criteria were
The restorative function of sleep
Because unrefreshing or nonrestorative sleep (NRS) is a hallmark of CFS, insights into the restorative function of sleep are mandatory. The present section gives an overview of our current understanding of this feature, while the next section expands on the construct of nonrestorative sleep.
Sleep is a universal phenomenon in living creatures. While sleep is conceived essential for normal life, its functions are as yet incompletely understood. Regarding non-rapid eye movement (NREM) sleep, most
Nonrestorative sleep
While adverse effects of sleep loss on daytime performance were already substantiated more than a century ago,34 medical attention for insomnia-like daytime symptoms in the presence of normal sleep duration is of a more recent date. The clinical phenomenon of interest is a subjective experience of unrefreshing sleep. Typically, patients report awakening unrestored or unrefreshed after a preceding night with sufficient sleep duration. From the 1970s on, unrefreshing sleep was observed as a
Sleep complaints and assessment of sleep in chronic fatigue and CFS
In all available case definition guidelines of CFS, sleep problems are described as a minor criterion (Table 1). The terms used vary substantially from (aspecific) sleep disturbance, to unrefreshing or nonrestorative sleep, to various aspects of sleep quality, sleep duration and elements of insomnia and/or hypersomnia. Evidently, the lack of uniformity in working definition mirrors the gap in our understanding of the pathophysiological role of sleep in CFS.
Sleep disturbance is reported by the
Acknowledgments
This work was supported by the scientific fund of the Department of Internal Diseases, Infectious Diseases and Psychosomatic Medicine.
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2018, Sleep Medicine ClinicsCitation Excerpt :Widespread pain and other symptoms of FM manifest on a severity spectrum and in the most severe cases, with profound inability to perform activities of daily living and work.1 More than half of women with FM meet criteria for chronic fatigue syndrome.34 Upwards of 70% of people with FM report sleep disturbances (difficulty falling and staying asleep, premature awakening, and fewer hours of sleep).1
Poor sleep quality is associated with greater circulating pro-inflammatory cytokines and severity and frequency of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) symptoms in women
2017, Journal of NeuroimmunologyCitation Excerpt :Research has revealed physiological manifestations of CFS/ME, such as dysregulated cortisol awakening response (CAR) and cytokine expression imbalance, which are associated with sleep disturbances in other contexts (Klimas and Koneru, 2007; Mariman et al., 2013; Wright et al., 2015). CFS/ME patients' sleep is typically reported as unrefreshing and/or frequently disturbed (Mariman et al., 2013). Recent research has identified subjective and objective accounts of poor sleep quality in CFS/ME—possibly identifying different sleep phenotypes (e.g. hypersomnia, insomnia-like phenotypes) (Gotts et al., 2013; Mariman et al., 2013).
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The most important references are denoted by an asterisk.