title: Heart rate variability in insomnia patients: A critical review of the literature.
abstract: Heart rate variability (HRV) is an objective marker that provides insight into autonomic nervous system dynamics. There is conflicting evidence regarding the presence of HRV impairment in insomnia patients. Web-based databases were used to systematically search the literature for all studies that compared the HRV of insomnia patients to controls or reported the HRV of insomnia patients before and after an intervention. 22 relevant papers were identified. Study characteristics were summarised, HRV measures were extracted and a risk of bias assessment for each study was performed. We were limited in our ability to synthesise outcome measures and perform meta-analyses due to considerable differences in patient (and control) selection, study protocols, measurement and processing techniques and outcome reporting. Risk of bias was deemed to be high in the majority of studies. As such, we cannot confirm that HRV is reliably impaired in insomnia patients nor determine the HRV response to interventions. Whilst HRV impairment in insomnia is a widely accepted concept, it is not supported by empirical evidence. Large longitudinal studies incorporating 24-hour recordings are required to elucidate the precise nature of HRV dynamics in insomnia patients.
authors.affiliation: Sydney Nursing School, University of Sydney, Australia; CIRUS, Centre for Sleep and Chronobiology, Woolcock Institute of Medical Research, University of Sydney, NSW, Australia.
authors.forename: Kirsty L
authors.initials: KL
authors.lastname: Dodds
authors.affiliation: CIRUS, Centre for Sleep and Chronobiology, Woolcock Institute of Medical Research, University of Sydney, NSW, Australia; Sydney Medical School, University of Sydney, Australia.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Miller
authors.affiliation: Sleep and Circadian Neuroscience Institute, Nuffield Department of Clinical Neurosciences, University of Oxford, England, UK.
authors.forename: Simon D
authors.initials: SD
authors.lastname: Kyle
authors.affiliation: Sydney Nursing School, University of Sydney, Australia; CIRUS, Centre for Sleep and Chronobiology, Woolcock Institute of Medical Research, University of Sydney, NSW, Australia.
authors.forename: Nathaniel S
authors.initials: NS
authors.lastname: Marshall
authors.affiliation: Sydney Nursing School, University of Sydney, Australia; CIRUS, Centre for Sleep and Chronobiology, Woolcock Institute of Medical Research, University of Sydney, NSW, Australia. Electronic address: christopher.gordon@sydney.edu.au.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Gordon
mesh_terms: D001341:Autonomic Nervous System / Q000502:physiology*; D015982:Bias; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications*
keywords: Autonomic nervous system; Heart rate variability; Hyperarousal; Insomnia; Review