Chronic fatigue and pain syndromes

Chronic fatigue syndrome (CFS) and fibromyalgia syndrome (FMS) are entirely based on symptom scores, either with abnormal fatigue or chronic pain as main symptoms. The case descriptions overlap significantly. Both are disabling illnesses with a significant health impact. All case definitions of both conditions include sleep disturbance. Both unspecified subjectively disturbed sleep and primary sleep disorders prove highly prevalent in CFS and FMS. Hence, biologically disturbed sleep can be hypothesized to play a role in their pathogenesis. In earlier studies polysomnography (PSG) has not shown significant objective differences between subjects with CFS and normal controls. More recent studies, and in particular systematic reviews and metaanalyses, have demonstrated features of an insomnia phenotype in both CFS and FMS, when subjective sleep difficulties are taken into account. Discrepancies between subjectively poor and objectively unremarkable sleep suggest a role for psychosocial factors to negatively affect perception of sleep quality or may be due to intra-individual day to day variability, not detected by a single night PSG. Whether or not insomnia is a presenting symptom of CFS or FMS versus an unrelated comorbid disorder is hard to ascertain, but cognitive behavourial therapy of insomnia has been shown to improve sleep quality and to reduce scores of fatigue and pain in these patients. Primary sleep disorders (PSD) are often detected in patients who otherwise qualify for a CFS and FMS diagnosis. Besides chronic insomnia, these disorders include obstructive sleep apnoea (OSA) and periodic limb movement disorder (PLMD). These conditions could independently contribute to daytime dysfunction. Causal treatment, e.g. PAP therapy for OSA, may lead to symptomatic improvement. However, medical evidence from the literature is not sufficiently robust to offer tools for predicting response to treatment of PSD in terms of improvement of fatigue or pain in individual patients. Multimodal biopsychosocial management is recommended for both CFS and FMS. Such approach takes into account the heterogeneity of these illnesses and acknowledges contributions of relevant biological, somnological, psychological and social factors in an individual patient history. In this perspective, primary sleep disorders may be a comorbid rather than an exclusionary condition with respect to CFS and FMS, that need to be screened for and adequately addressed