title: Heart rate variability and endothelial function after sleep deprivation and recovery sleep among male         shift and non-shift workers.
abstract: OBJECTIVE
  Endothelial dysfunction and alterations in heart rate variability (HRV) as well as sleep deprivation and shift work have been associated with cardiovascular disease. The aim of this study was to compare HRV and endothelial function among shift and matched non-shift workers in response to total sleep deprivation and recovery sleep under identical laboratory settings.
  
  
  METHODS
  Eleven experienced male shift workers (shift work ≥ 5 years) and 14 non-shift workers were matched for age, body mass index, and cholesterol. HRV parameters [eg, HR variance and low frequency/high frequency (LF/HF) ratio] were derived from 5-minute electrocardiogram bins at 0.25, 4.25, 11.5, 12.5, and 13.5 hours after habitual wake-up time and endothelial function was assessed by flow-mediated dilatation (FMD) using ultrasound at 0.75 and 10.75 hours after habitual wake-up time, following baseline sleep, total sleep deprivation, and recovery sleep (posture- and food-controlled throughout). Circadian phase was assessed before baseline sleep by salivary dim light melatonin onset.
  
  
  RESULTS
  There was no difference in circadian phase between shift and non-shift workers. HR variance was highest at 0.25 hours following total sleep deprivation and lowest after recovery sleep. A significantly higher LF/HF ratio, significantly lower HR variance, and a trend for a lower %FMD (P=0.08) were observed among shift compared to non-shift workers.
  
  
  CONCLUSIONS
  Despite similar demographics, circadian phase, posture and food intake, differences in endothelial function and HRV were observed in the two groups, which may reflect higher sympathetic and/or lower parasympathetic activity, contributing to increased cardiovascular risk among the shift workers.
authors.affiliation: Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK. sophie.wehrens@surrey.ac.uk
authors.forename: Sophie M T
authors.initials: SM
authors.lastname: Wehrens
authors.forename: Shelagh M
authors.initials: SM
authors.lastname: Hampton
authors.forename: Debra J
authors.initials: DJ
authors.lastname: Skene
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000209:etiology*; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology*; D004730:Endothelium, Vascular / Q000473:pathology* / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010275:Parasympathetic Nervous System / Q000473:pathology; D017286:Polysomnography / Q000295:instrumentation; D012044:Regression Analysis; D012892:Sleep Deprivation / Q000150:complications* / Q000473:pathology; D013223:Statistics as Topic; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology; D014940:Work Schedule Tolerance / Q000502:physiology*