title: The influence of age on heart rate variability during morning wakefulness.
abstract: OBJECTIVE
  Early morning wakefulness is associated with a peak in cardiac events. The influence of ageing on cardiac regulation during this time is unknown. This cross-sectional study of healthy men and women (n = 40, 20-30 and >60 years) investigated the effect of age on heart rate variability (HRV) during morning versus evening wakefulness and sleep.
  
  
  METHODS
  Stable electrocardiogram data during each wake period and sleep stage was analysed using power spectral analysis. HRV measurements were assessed using two (young, older) by two (male, female) ANOVAs with repeated measures on wake/sleep stage.
  
  
  RESULTS
  Young adults experienced increased low-frequency power and low-frequency/high-frequency ratios during morning wakefulness versus slow wave sleep (p < 0.01). Older adults did not show any variation in any HRV variables across wake and sleep stages. All effects were independent of gender.
  
  
  CONCLUSIONS
  Older adults did not experience increased sympathetic dominance during morning wakefulness; thus in the older population, fluctuations in autonomic control, indicated by HRV measurements, are unlikely to account for increased occurrence of cardiac events at this time.
authors.affiliation: Clinical and Academic Unit of Sleep and Ventilation, Royal Brompton Hospital, Imperial College, Fulham Road, London SW3 6NP, UK. e.goff@imperial.ac.uk
authors.forename: Elizabeth Anne
authors.initials: EA
authors.lastname: Goff
authors.forename: Christian L
authors.initials: CL
authors.lastname: Nicholas
authors.forename: Anura S
authors.initials: AS
authors.lastname: Malaweera
authors.forename: Anita K
authors.initials: AK
authors.lastname: Simonds
authors.forename: John
authors.initials: J
authors.lastname: Trinder
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Morrell
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D003430:Cross-Sectional Studies; D004569:Electroencephalography; D004576:Electromyography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D017286:Polysomnography; D012129:Respiratory Function Tests; D018401:Sample Size; D012727:Sex Characteristics; D012890:Sleep / Q000502:physiology; D012895:Sleep, REM / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology; D014851:Wakefulness / Q000502:physiology*; D055815:Young Adult