Objective: Patients with fibromyalgia syndrome (FM) complain of inadequate sleep, which could contribute to common symptoms including sleepiness, fatigue, or pain.
However, measures that consistently and objectively distinguish FM patients remain elusive.
Methods: Fifteen women with FM and 15 age- and gender-matched controls underwent 3 nights of polysomnography; Multiple Sleep Latency Tests to assess sleepiness; testing of auditory arousal thresholds during non-REM stage 2 and stage 4 sleep; overnight assessment of urinary free cortisol; and analysis of 24-hour heart rate variability.
Results: On the second night of polysomnography, women with FM in comparison to controls:
• Showed more stage shifts (p = 0.04) but did not differ significantly on any other standard polysomnographic measure or on the Multiple Sleep Latency Tests.
• Alpha EEG power during deep non-REM sleep, alone or as a proportion of alpha power during remaining sleep stages, also failed to distinguish the groups, as did auditory arousal thresholds.
• Urinary free cortisol did not differ between FM and control subjects in a consistent manner.
• However, decreased short-term heart rate variability (HRV) and especially ratio-based HRV among FM subjects suggested diminished parasympathetic and increased sympathetic activity, respectively. [The autonomic nervous system has two balancing or opposing parts: the parasympathetic nervous system is responsible for physiological resting & restoring functions, and the sympathetic nervous system is responsible for stress-response effects.]
• Other HRV measures suggested decreased complexity of HRV among the FM subjects.
Conclusion: Standard measures of sleep, a gold-standard measure of sleepiness, quantified alpha-delta EEG power, auditory arousal thresholds, and urinary free cortisol largely failed to distinguish FM and control subjects.
However, heart rate variability analyses showed more promise, as they suggested both increased sympathetic activity and decreased complexity of autonomic nervous system function in FM.
Source: Journal of Rheumatology, Aug 14, 2009. PMID: 19684146, by Chervin RD, Teodorescu M, Kushwaha R, Deline AM, Brucksch CB, Ribbens-Grimm C, Ruzicka DL, Stein PK, Clauw DJ, Crofford LJ. Sleep Disorders Center, Department of Neurology, and Division of Rheumatology, Department of Internal Medicine, University of Michigan, Ann Arbor; Wisconsin Sleep Institute and Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, University of Wisconsin, Madison; Washington University School of Medicine, St. Louis, Missouri; Division of Rheumatology, Department of Internal Medicine, University of Kentucky, Lexington, USA. [E-mail: firstname.lastname@example.org]