Poor quality and unrefreshing sleep is one of the most common symptom complaints in Chronic Fatigue Syndrome (CFS). Despite this, the links between sleep dysfunction and CFS are not well understood, and there has been an absence of good quality research into the nature of sleep problems in CFS, which also lack consistency in the data reported. However, it remains plausible that sleep problems may help to maintain and exacerbate other existing symptoms. Given the dispute in models ranging from the biological to the psychological, competing to explain symptomology, it is a critical time by which we try to understand the relationship between poor sleep, fatigue, endocrine activity and CFS, in an attempt to shortcircuit this debate. With an aim to redress this, this thesis intended to examine the role of sleep from several angles, utilizing a range of assessment methods; Study 1 addressed the lack of in depth qualitative interview studies, to understand the extent to which sleep, its management and problems, are linked to the lived experience of CFS, and how it interacts with other symptoms (chapter 3). Patient narratives demonstrated that sleep disturbances experienced were highly unpredictable and variable over time, but played a key role in symptom maintenance; Study 2 examined self-reported sleep (via sleep diaries) in CFS patients, exploring whether sleep quality and daytime napping had an impact on daytime fatigue, sleepiness and cognitive functioning (key dimensions of the illness experience) (chapter 4). The results were highly variable but indicated that afternoon-evening napping was associated with greater impairment in daytime cognitive functioning in CFS patients. It was also evident that CFS patients with longer wake time and a shorter diagnosis had more severe fatigue; Study 3 explored the possibility that sleep problems in this population are not homogeneous and revealed four sleep-specific phenotypes to exist, which are amenable to different treatment approaches. The initial cross-sectional examination of single-night polysomnography (PSG) data identified 30% of the sample had a primary sleep disorder (PSD), which underscores the need to assess for PSDs in CFS populations (chapter 5); Study 4 was conducted to address the principle aim of this thesis; to determine the feasibility of a detailed, 3-night sleep assessment protocol in a small cohort of CFS patients. By utilising iv a range of methods including ambulatory PSG and a gold-standard protocol for sampling of diurnal salivary cortisol, the study piloted the most comprehensive assessment of sleep ever attempted in a CFS population. The findings established a successful protocol that was acceptable to patients (chapter 6), a key advancement in this field where effective and thorough sleep assessment is needed. Preliminary sleep data confirmed a notable variability of sleep problems to exist. Further, the temporal stability of sleep variables was established; sleep continuity (sleep duration, wake duration, sleep efficiency) and main architectural (sleep stages) parameters were consistent across two nights of assessment (chapter 7). The results presented in this thesis indicate that disturbed sleep is a major problem for patients with CFS, albeit highly variable between and within individuals. The identification of sleep phenotypes also confirms the heterogeneity of sleep in CFS. Interestingly, light sleep and arousability was a recurring sleep characteristic in patients that was mirrored by the studies presented throughout the thesis, highlighting a potential autonomic component. This should be a consideration for forthcoming work, along with the possibility that sleep disturbances may mediate the maintenance and exacerbation of symptoms, fuelling a reciprocal cycle that keeps the condition going. The preliminary findings presented throughout this trajectory of research will help to form the systematic development of a sleep characterisation and intervention programme. With this field moving towards more patient-centred medicine and tailored treatments, by combining data from the objective and subjective sleep measures, we aim to design a definitive multicentre study, using sleep-specific interventions, amenable to the four phenotypes identified. The long-term goal is to improve treatments that will enhance symptom management, which is crucial in this condition, at least until the CFS research understands the pathogenesis of this debilitating disease.
|Publication status||Accepted/In press - Apr 2014|