Seasonal Changes in Heart Rate Variability in 11- to 13-Year-Old Girls

Abstract

Assessment of the heart rate variability (HRV) in healthy subjects and patients has been widely used in clinical practice and physiological studies [1][2][3]. Yet, interpretation of the nature of HRV, as well as issue of the normal ranges of the standard indices of HRV, is still challenging. This is because of the absence of a single, unified system for processing HRV parameters. At present, there are few data on the relationship between the HRV and gender, age, and chronobiological factors. Analysis of the seasonal changes in HRV in 7-to 9-year-old boys and girls from Izhevsk has shown that the HRV is usually lower in autumn than in spring, thereby indicating that sympathetic tone is higher in autumn than in spring [4]. The objective of this work was to study the seasonal changes in HRV in 11-to 13-year-old girls. METHODSLongitudinal studies were performed with 90 girls aged 11 ( N = 31), 12 ( N = 28), and 13 ( N = 31) to record their HRV parameters at 3-month intervals in winter, spring, summer, and autumn and simultaneously assess their puberty by the development of secondary sexual characteristics and the menstrual cycle.A Valenta computer-integrated medical diagnostic system (St. Petersburg, PO NEO) was used to record the lead II ECG in the supine position with subsequent analysis of 500 cardiac cycles. The system made it possible to automatically process the length of RR intervals and calculate 23 HRV indices (described in detail in [2]), which are consistent with those recommended by the European Society of Cardiology and the North American Society of Pacing and Electrophysiology [1, 2].The following indices were calculated: mathematical expectation ( M , ms); maximum ( RR max ) and minimum ( RR min ) RR intervals (ms); variance (ms 2 ); standard deviation (ms); coefficient of variation (%); mode (Mo, ms); mode amplitude (AMo, %); variation range (VR, ms 2 ); power (ms 2 ) of high frequency (HF) fluctuations (0.5-0.1 Hz); normalized HF power, i.e., relative HF power in proportion to the sum of the HF and low frequency (LF) powers; power (ms 2 ) of LF fluctuations (0.1-0.03 Hz); normalized LF power, i.e., relative LF power in proportion to the sum of the HF and LF powers; power (ms 2 ) of very low frequency (VLF) fluctuations (less than 0.03 Hz); LF/HF, VLF/HF, and (VLF + LF)/HF ratios, or the index of centralization; the coefficient of correlation between HF and respiratory waves (%); the coefficient of monotony [2]; the index of tension (IT) of regulatory systems calculated as IT = AMo/(2VR × Mo); the triangular index, i.e., the ratio between the total number of RR intervals and the number of intervals with the most common length, expressed in technical units [2]; the differential index (DI) of rhythm calculated aswhere i is the number of the current interval, low values of which are indicative of high HRV [2]; and the relative number of successive RR intervals differing by more than 50 ms in proportion to the total number of cardiac intervals ( pRR 50 , %).The results of the study were statistically anal...

Long-Term Tracking of a Patient’s Health Condition Based on Pulse Rate Dynamics During Sleep

“…Previous articles have discussed both short-term and long-term biorhythms of HRV and PRV, as well as their nonlinearities. 11,17,18,24,32 We are also trying to explore effective approaches to track this lifelong biorhythm and to depict the orbit of health condition. 7,8 In this study, a seasonal variation embedded within a downward trend is observed in the patient that might imply a decreasing in humans' adaptation to the external environment or an intrinsic deterioration caused by either physical conditions or pathophysiological factors.…”

“…11,17,19,24,32 However, most of the observations used intermittent data collected monthly or seasonally by ambulatory electrocardiogram (AECG) monitoring. 17,19,24 Few of them were taken from continuous daily collected data. 11 Traditional measurements based on AECG monitoring are clearly not suitable for daily application over a long-term period because of their high cost, complex procedures, poor usability, and discomfort.…”