Correlations between Sleep Disturbances and Pain in Fibromyalgia: An Updated Review

Abstract

Abstract Fibromyalgia (FM) is a common condition characterized by chronic musculoskeletal pain. Sleep disturbances, such as reduction of Slow Wave Sleep (SWS) and alpha wave intrusion in non-Rapid Eye Movement (non-REM) sleep, are a main feature of FM and are related to alterations of central nervous system, autonomic nervous system and endocrine system. Improving sleep quality can significantly reduce patient reported symptoms. Polysomnographic findings support the hypothesis of a vicious circle of sleep disturbances, impaired sympathetic and nociceptive pathways and chronic pain. Despite better understanding of underlying pathophysiological processes, there is currently limited data about effectiveness of available pharmacological therapies for sleep. All the three drugs currently licensed by US Food and Drug Administration (FDA) and European Medicines Agency (EMA) for treating FM (duloxetine, milnacipran and particularly pregabalin) can improve sleep quality in these patients. Other drugs, like gabapentin, sodium oxybate, cyclobenzaprine and cannabinoids, can be beneficial for FM-related sleep disturbances, but more evidence needs to be collected for their use to be possibly recommended. Non-pharmacological treatments aimed at improving sleep hygiene can still be considered the mainstay intervention for sleep disturbances in FM, relying on an all-round assessment of patients’ clinical history and comorbidities. Further studies are needed to fully investigate efficacy and safety of promising therapies. Keywords Fibromyalgia; Sleep; Non-restorative sleep; Polysomnography; Pain management; Autonomic nervous system Abbreviations FM: Fibromyalgia; EEG: Electroencephalography; EMG: Electromyography; EOG: Electrooculography; REM: Rapid Eye Movement; SWS: Slow Wave Sleep; CAP: Cyclic Alternating Pattern; PLM: Periodic Limbs Movements; CNS: Central Nervous System; fMRI: functional Magnetic Resonance; 5-HT: 5-Hydroxytryptamine; HR: Heart Rate; HFRR: High Frequency component of RR variability; GH: Growth Hormone; IGF-1: Insulin-like Growth Factor-1; OSA: Obstructive Sleep Apnea; GERD: Gastroesophageal Reflux Disease; THC: delta-9Tetrahydrocannabinol; CB1: Cannabinoid receptor type 1