Patients with fibromyalgia reported poorer subjective sleep quality compared with controls, although accelerometry parameters showed no significant differences between groups.
Although patients with fibromyalgia reported poorer subjective sleep quality compared with controls, no significant differences in objective physiological determinations were observed, according to a study published in biomedicines.1 Investigators believe a dysregulation of the stress response could be linked to the delay in resting circadian rhythm and lead to difficulty falling asleep, which would therefore cause the perceived lack of rest and fatigue upon waking.
Poor sleep quality can increase the severity of symptoms associated with fibromyalgia, including nonspecific pain and approximately two thirds of patients report sleep disturbances as well as cognitive and mood alteration. Unfortunately, this repetitive cycle of decreased sleep and increased pain often afflicts this patient population. Patients experiencing poor sleep were more likely to report worsening depression, emotional distress, and difficulties with attention and memory.2
“Although numerous precedents have highlighted the role of sleep in this syndrome, the substantial importance of sleep disturbances and sleep quality has only recently been recognized in the etiology of fibromyalgia,” wrote Maria Dolores Hinchado, PhD, associated with the Immunophysiology Research Group, Universitario de Investigación Biosanitaria de Extremadura (INUBE), Spain, and colleagues. “In fact, the American College of Rheumatology (ACR) proposed a modification to the diagnostic criteria for fibromyalgia in 2010, which, in addition to removing trigger points, emphasized the assessment of the severity of sleep problems and fatigue.”
Perceived sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) in 68 patients with fibromyalgia as well as an age-matched reference group of 68 healthy controls. Objective sleep quality was evaluated using accelerometry and systemic concentrations of sleep-related hormones, including melatonin, serotonin, oxytocin, and catecholamines, were determined in the second portion of the study using smaller subgroups comprised of patients (n = 11) and controls (n =11). Accelerometry measured objective parameters related to sleep quality, such as efficiency (the ratio of total sleep time and time in bed), latency (the time it takes to fall asleep), in-bed and out-bed times, wake after sleep onset, the number of awakenings, and the daily lux average counts.
Patients in the fibromyalgia cohort reported poorer subjective sleep quality when compared with the control group. However, accelerometry parameters showed no significant differences between groups, apart from a delay in getting in and out of bed. Further, patients with fibromyalgia had a lower serotonin/melatonin ratio (hormones responsible for the sleep/wake cycle) and did not have any significant differences in oxytocin concentration (the hormone related to sleep quality, pain, and depression) or the adrenaline/noradrenaline ratio. Therefore, the poor perception of sleep reported by patients with fibromyalgia did not correspond to the objective determinations.
Investigators believe the subjective perception of poor sleep quality could be linked to a reduced physiological and psychological capacity to regulate stress responses. This could manifest in delayed bedtime and wake-up times in addition to a decreased serotonin/melatonin ratio, which is generally more compatible with nocturnal levels in healthy people.
The small sample size included in the second portion of the study was considered a limitation. Investigators urge future studies to incorporate more patients and evaluate all objective biomarkers, particularly melatonin, over a greater number of hours.
“The results of this pilot study in a group of patients diagnosed with fibromyalgia may contribute to a better understanding of the pathophysiology and etiology of this syndrome, particularly in relation to sleep and, therefore, to perceived fatigue,” investigators concluded.