title: The relationship between slow-wave activity, body temperature, and cardiac activity during nighttime sleep.
abstract: OBJECTIVE
  Recent work indicates that cardiac sympathetic activity is not influenced by the circadian system and instead decreases after sleep onset. However, little is known about the pattern of change in cardiac sympathetic activity during NREM/REM sleep cycles and whether this is associated with alterations in slow-wave activity (SWA). To address these questions, we examined SWA, cardiac sympathetic activity, heart rate and rectal and foot temperatures during the first three NREM/REM sleep cycles and during transitions between NREM and REM sleep.
  
  
  METHODS
  Subjects were required to maintain a constant sleep-wake cycle for at least a week and have at least one adaptation night, before their night of recording.
  
  
  METHODS
  Individual temperature controlled bedrooms.
  
  
  METHODS
  10 young healthy males and females.
  
  
  METHODS
  NA.
  
  
  RESULTS
  All variables showed the greatest change in the first NREM cycle. Specifically, SWA, sympathetic activity, heart rate and foot temperature increased while rectal temperature decreased. After the initial increase, cardiac sympathetic activity decreased across the sleep phase, in association with a decrease in heart rate. Cardiac sympathetic activity did not significantly alter across NREM-REM cycles.
  
  
  CONCLUSIONS
  The results suggest that increases in heart rate and cardiac sympathetic activity early in the sleep period are, in part, a compensatory reaction to the concomitant thermoregulatory changes observed. These results also indicate that the effect of time asleep on cardiac sympathetic activity may be greater than the influence of sleep cycles. These results are discussed with reference to the recuperative value of naps.
authors.affiliation: Centre for Sleep Research, Queen Elizabeth Hospital, University of South Australia. hburgess@rush.edu
authors.forename: H J
authors.initials: HJ
authors.lastname: Burgess
authors.forename: A L
authors.initials: AL
authors.lastname: Holmes
authors.forename: D
authors.initials: D
authors.lastname: Dawson
mesh_terms: D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004562:Electrocardiography; D005260:Female; D005528:Foot / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012007:Rectum / Q000502:physiology; D012890:Sleep / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D013997:Time Factors