Original Article Gender specificity of the slow wave sleep lost in chronic widespread musculoskeletal pain Gilles J. Lavigne a,b,⇑ , Kazuo Okura a,b,c , Susumu Abe a,b,d , Roberto Colombo e , Nelly Huynh a,b , Jacques Y. Montplaisir b,f , Serge Marchand g , Paola A. Lanfranchi b,f,h a Faculté de médecine dentaire, Université de Montréal, Canada b Centre d’étude du sommeil, Hôpital du Sacré-Cœur de Montréal, Canada c Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan d Department of Oral Care and Clinical Education, The University of Tokushima, Japan e Department of Bioengineering, Salvatore Maugeri Foundation, Veruno, Italy f Faculté de médecine, Université de Montréal, Canada g Faculté de médecine, Université de Sherbrooke, Canada h Department of cardiology, Hôpital Sacré-Coeur de Montreal, Canada article info Article history: Received 8 April 2010 Received in revised form 20 July 2010 Accepted 27 July 2010 Available online 21 January 2011 Keywords: Chronic widespread pain Sleep and pain Napping Slow wave activity Sleep intensity Delta activity Electroencephalography Heart rate variability abstract Objectives: The majority of patients suffering from musculoskeletal chronic widespread pain (CWP) are females, and they tend to report poor sleep. We tested the hypothesis that the poor sleep of female patients reporting CWP is gender specific for changes in (1) electroencephalograph (EEG) features and (2) heart rate variability (HRV). Methods: Twenty-four normal sleepers were compared to 24 patients with CWP who complained of poor sleep. Patients were referred from general practice and were matched for age (41–47 years) and gender (25 W, 23 M). Sleep variables and spectral EEG activity analyses were performed during 1 night of sleep recording. Time-domain cardiac RR interval and spectral autoregressive analyses were also performed from the same data set. Results: Compared to normal females, female patients with CWP had significantly shorter sleep duration (À68 min), lower sleep efficiency (À9.9%), twice the awakenings and a trend for more periodic limb movements per hour of sleep. Daytime napping was reported by 78% of CWPs. Compared to all controls, females with CWP had significantly less power in the EEG delta band in the first and second non-REM sleep cycle. Although RR interval analysis revealed that CWP patients had a faster heart rate, neither the sympathetic nor sympathovagal analysis reached statistical significance for gender or pain status comparisons. Conclusions: Female CWP patients have shorter sleep duration with many awakenings and lower sleep EEG delta activity without gender difference in HRV. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction About 1 in 4 adults in the general population report chronic pain lasting for at least 3 months [1–6]. Poor sleep and pain inter- action can be bidirectional or circular in chronic pain patients. Moreover, a poor night of sleep can be followed by more pain the next day, and a day with more pain can be followed by a night of poor sleep [7]. Chronic widespread musculoskeletal pain, a sensory condition afflicting several body sites, is experienced by about 8–12% of the population, with females accounting for as much as 80% of this group [8,9]. In general medical practice, the risk (odds ratio) that a chronic widespread musculoskeletal pain (CWP) patient will report poor sleep quality and fatigue is 3.1 and 3.5 times higher than in control subjects, respectively [10]. Patients with CWP, i.e., clinically diagnosed with fibromyalgia, report poor quality sleep, which may be due to increased awakenings, transient sleep arous- als, and disrupted delta sleep or sleep stage N3 [11–14]. A recent comparative study on the sleep macrostructure revealed that female patients with fibromyalgia had more sleep stage shifts and longer stage N2 sleep duration, possibly due to more rapid transition toward sleep stage N3, a variable that also contributed to explain higher pain reports the next day [15]. The power of SWA over consecutive non-REM to REM sleep cycles is used to estimate sleep homeostasis and regulation by means of 1389-9457/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.sleep.2010.07.015 ⇑ Corresponding author. Address: Faculté de médecine dentaire, Université de Montréal, CP 6128 Succursale Centre-Ville, Montréal, Québec, Canada H3C 3J7. Tel.: +1 514 343 2310; fax: +1 514 343 2233. E-mail address: gilles.lavigne@umontreal.ca (G.J. Lavigne). Sleep Medicine 12 (2011) 179–185 Contents lists available at ScienceDirect Sleep Medicine journal homepage: www.elsevier.com/locate/sleep