SLEEP AND BLOOD-PRESSURE - SPONTANEOUS BAROREFLEX SENSITIVITY IN DIPPERS AND NON-DIPPERS

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 t o ascertain whether there is a difference between 24 h BRS values in d ippers and non-dippers that might account for the difference in noctur nal blood pressure behaviour. Design In a group of consecutive untreat ed hypertensive patients undergoing 24 h ambulatory intra-arterial blo od pressure (IABP) monitoring, 18 were non-dippers i.e., their mean IA BP during sleep failed to drop by 10% of their waking IABP. Each non-d ipper was matched for age and waking IABP with two dippers, The BRS ha d previously been assessed with the 'Oxford' bolus phenylephrine techn ique; spontaneous BRS was assessed throughout the 24 h period by off-l ine computer analysis of spontaneous Variations in IABP and R-R interv al. Results In both groups there was a significant increase in spontan eous BRS during sleep (P<0.0001 for dippers, P<0.0001 for non-dippers) . There was no significant difference between spontaneous BRS in dippe rs and non-dippers, when they were either awake or asleep. Conclusion 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 h ypertensives and are not likely to contribute to the normally observed nocturnal fall in blood pressure.