Association between the impairment of skin temperature rhythm and hypertension

Abstract

An increasing amount of bibliography relates hypertension to certain sleep disorders and reduced sleep quality. Wrist temperature (WT) circadian rhythm is related to autonomic balance, thermoregulation, sleep propensity and sleep wake cycle; hence, it has been proposed as possible screening technique to assess blood pressure (BP) dipping status. Thus, the aim of this work is to determine of hypertension is associated to changes in WT rhythm. 33 healthy subjects (21–63 years old) were monitoring for WT, Activity (A) and Position (P) by means of two data loggers, an Ibuttom device (ThermoChron®, Data loggers I- button) 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 considered when P < 30 o and A < 20 o /min. Hypertensive patients showed increased heart rate when were compared with normotensive patients (79.94 ± 2.76 bpm vs. 71.00 ± 1.84 bpm, p < 0.05) and a significant decrease in WT during sleep period (34.22 ± 0.14 o C vs. 34.63 ± 0.09 o C, p < 0.05) and lower position values during daytime (47.83 ± 1.97 o vs. 52.57 ± 1.23 o , p < 0.05) respect to normotensive subjects, while no differences were founded in activity and TAP. Hypertension is closely related to a significant impairment in WT circadian rhythm, allowing differentiating between normotensive and hypertensive patients. In fact, lower nighttime WT values are connected to sleep disorders such as insomnia or sleep disordered breathing, which are related to higher nighttime blood pressure probably due to the increase in nocturnal sympathetic activation in hypertensive patients. 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).