Non dipping blood pressure pattern is related to an increase in daytime distal skin temperature

Abstract

Introduction The circadian pattern of blood pressure (BP) is closely associated to sleep-wake cycle, target organs damage and cardiovascular events. Thus, BP circadian pattern diagnosis should be based on an objective procedure to determine patient’s actual sleep and wake time instead of standard sleep schedules. Wrist temperature (WT) rhythm is subordinated to the master circadian clock and it is related to autonomic balance, thermoregulation, sleep propensity and sleep wake cycle and also responds to postural changes. Thus, the purpose of this research is to determine accurately the BP pattern using circadian ambulatory monitoring and the association between WT rhythm and the BP dipping status. Materials and methods WT, Activity (A) and Position (P) were recorded during five days in 33 healthy subjects, aging from 21 to 63 years old, by means of two data loggers, an Ibuttom device (ThermoChron®,) and a Hobo actimeter (Hobo® Pendant G, Acceleration Data Logger). Ambulatory BP was determined during 24 h using a BP monitor (Spacelabs® Medical) with a sampling rate of one measure every 20 min during day and every 40 min during night. An alertness variable (TAP) was calculated averaging normalized values for WT, A and P. Sleep time was automatically considered when P 30 o and A 25 o /min. Results Non-dipper subjects showed higher systolic BP during nighttime (124.62 ± 6.00 mmHg vs 112.36 ± 2.50 mmHg) as it was expected. In addition, we found a significant increase in WT during daytime (33.81 ± 0.18 o C vs 32.88 ± 0.19 o C), but not during nighttime, and higher TAP values during nighttime (0.19 ± 0.03 a.u. vs. 0.14 ± 0.01 a.u.) in non-dipper compared with dipper subjects, while no differences were found for activity and body position. Conclusion Considering individual sleep pattern when evaluating BP pattern provides a more accurate diagnosis of dipping pattern. The use of P, A and WT information might change the interpretation of ambulatory BP monitoring data and improve the diagnosis of circadian BP pattern. Furthermore, circadian monitoring could distinguish between dipper and non-dipper pattern using daytime WT values. Acknowledgements Study supported by RETICEF (RD12/0043/0011), MINECO (BFU2010–21945-C02–01), and INNPACTO (IPT-2011–0833-900000) with FEDER cofounding to JAM, and a research fellowship to Antonio Martinez-Nicolas (University of Murcia).