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Parasympathetic function is important in the induction and maintenance of sleep. We examined whether nocturnal vagal modulation of heart rate is related to the poor sleep quality commonly reported in chronic fatigue syndrome (CFS). [The vagus nerve is attached to the brain stem and branches down through the neck, chest and abdomen. It is chief autonomic regulator and ‘pacemaker’ of the heart, viscera, and other organs.]
Heart rate (HR, as R-R intervals) was continuously monitored during sleep in 20 patients with CFS and 20 matched control subjects. Questionnaires assessed demographic information, symptoms, functional impairment, and subjective sleep quality.
CFS was associated with more sleep problems in general and poorer subjective sleep quality on the study night (all p < 0.003), And reports of repeated awakening during the night were 7 times more likely compared to healthy subjects (p = 0.017). Time and frequency-domain parameters of HR variability during sleep were significantly lower in patients with CFS (all p < 0.006). Multiple regression analyses revealed that heart rate variability (HRV) parameters were the best predictors of subjective sleep measures. This study identified significant reductions in vagal modulation of heart rate during sleep in CFS. Low HRV strongly predicted sleep quality-suggesting a pervasive state of nocturnal sympathetic hypervigilance in CFS. Source: Experimental Brain Research, May 26, 2010. PMID: 20502886, by Burton AR, Rahman K, Kadota Y, Lloyd A, Vollmer-Conna U. School of Psychiatry; Centre for Infection and Inflammation Research, School of Medical Sciences; Department of Human Behaviour, University of NSW, Sydney, Australia. [Email: firstname.lastname@example.org]