Cardiovascular regulation in female students of northern university during extreme photoperiod seasons

Abstract

Objective. The aim of study was to assess the state of cardiovascular system in female students in the northern region during the seasons with extreme photoperiod. Design and methods. The study was conducted in Nizhnevartovsk, Khanty-Mansi Autonomous Okrug-Yugra (a region equated to the Far North) in the seasons with extreme values of photoperiod. The female students of Nizhnevartovsk State University (n = 73) aged 18-21 years were examined. Anthropometric measurements were carried out. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were recorded automatically using UA-101 model tonometer. Pulse and mean dynamic pressure were calculated according to Hickam's formula. On the basis of HR we determined the average duration of cardiac cycle. Autonomic tone was assessed according to calculated Kerdo index (KI). We used CardioVisor-06c to determine the prenosological state of cardiac activity. Results. There was a significant increase in body weight in the short daylight period. The HR during the long daylight period was significantly higher than during light deprivation, leading to a shorter cardiac cycle duration. Seasonal dynamics of blood pressure characteristics were not evident, although during “white nights” at least 10 % female students had SBP higher than 130 mm Hg, and maximal SBP reached 135 mm Hg. KI values demonstrated significant changes in autonomic tone. During short daylight hours average characteristics of KI were negative and reflected activity of parasympathetic activity. Increase of sympathetic influences was during longer daylight hours. During “biological twilight” “Myocardium” index was significantly lower than during white nights. During short daylight hours only 10 % students showed “Myocardium” index over normal values (15 %), while half of respondents had higher values during white nights. “Rhythm” index was normal during the short daylight hours and significantly higher during the long daylight hours, only 10 % participants had normal values. Conclusions. The analysis of electrophysiological parameters of myocardium showed seasonal changes in female students and “white nights” were associated with more negative effects than “biological twilight”. During “white nights” we showed increase in integral indices of dispersion mapping, increase in resting HR and KI.