title: Sleep and blood pressure: spontaneous baroreflex sensitivity in dippers and non-dippers.
abstract: OBJECTIVE
  Baroreflex sensitivity (BRS) increases during sleep, whereas arterial blood pressure falls. Some hypertensive patients do not have a nocturnal fall in blood pressure (non-dippers). The objective was to ascertain whether there is a difference between 24 h BRS values in dippers and non-dippers that might account for the difference in nocturnal blood pressure behaviour.
  
  
  METHODS
  In a group of consecutive untreated hypertensive patients undergoing 24 h ambulatory intra-arterial blood pressure (IABP) monitoring, 18 were non-dippers i.e., their mean IABP during sleep failed to drop by 10% of their waking IABP. Each non-dipper was matched for age and waking IABP with two dippers. The BRS had previously been assessed with the "Oxford' bolus phenylephrine technique; spontaneous BRS was assessed throughout the 24 h period by off-line computer analysis of spontaneous variations in IABP and R-R interval.
  
  
  RESULTS
  In both groups there was a significant increase in spontaneous BRS during sleep (P < 0.0001 for dippers, P < 0.0001 for non-dippers). There was no significant difference between spontaneous BRS in dippers and non-dippers, when they were either awake or asleep.
  
  
  CONCLUSIONS
  BRS did not differ significantly between dippers and non-dippers, when they were either awake or asleep. Changes in BRS during sleep are not likely to account for the abnormal dipping pattern in a minority of hypertensives and are not likely to contribute to the normally observed nocturnal fall in blood pressure.
authors.affiliation: University of Birmingham, Department of Cardiovascular Medicine, UK.
authors.forename: J C
authors.initials: JC
authors.lastname: Vaile
authors.forename: T J
authors.initials: TJ
authors.lastname: Stallard
authors.forename: M
authors.initials: M
authors.lastname: al-Ani
authors.forename: P J
authors.initials: PJ
authors.lastname: Jordan
authors.forename: J N
authors.initials: JN
authors.lastname: Townend
authors.forename: W A
authors.initials: WA
authors.lastname: Littler
mesh_terms: D000328:Adult; D000368:Aged; D006801:Humans; D008875:Middle Aged; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology*; D012018:Reflex; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012890:Sleep / Q000502:physiology*
chemical_list: D010656:Phenylephrine