Chronobiological changes in arterial blood pressure in participants of the 5^th and 6th Czech Antarctic Scientific Expeditions

OBJECTIVE: To evaluate potential changes in arterial blood pressure (ABP) and heart rate (HR) during a 2-month stay in Antarctica, using chronobiological analysis. METHODS: An observational study performed at Mendel research base, Antarctica, during 2011 and 2012. The studied group consisted of 24 participants of the 5^th and 6^th Czech Antarctic Scientific Expeditions. Three series of 24-hour ABP monitoring were performed, of these two in Antarctica and one in the Czech Republic. Chronobiological analyses of the data were performed (Halberg Chronobiology Center, Minnesota) using population-mean cosinor. The values of MESOR (Midline Estimating Statistic Of Rhythm), double amplitude and the acrophase were obtained for SBP (Systolic Blood Pressure), DBP (Diastolic Blood Pressure) and HR. These rhythm characteristics were compared between the two locations by parameter tests and by the paired f-test. RESULTS: On the average, the MESORs of SBP, DBP and HR were significantly higher in Antarctica than in the Czech Republic, as were the double amplitudes of the 12-hour component of SBP and DBP. High prevalence of CHAT (Circadian Hyper-Amplitude-Tension) was detected in Antarctica (8/24 = 33%); only 2 persons had CHAT in the Czech Republic (χ²=3.945, p=0.047). CONCLUSIONS: A prolonged stay in Antarctica clearly affected certain chronobiological parameters of ABP and HR.