Intra-individuals and inter- and intra-observer reliability of short-term heart rate variability in adolescents

Background: To examine the reliability of heart rate variability (HRV) parameters in adolescents and to analyse the inter-and intra-observer reliability of data analysis. Methods: The sample included 27 adolescents aged 14-19 years old. RR intervals were obtained for 10 min in the supine position on two different days (Day 1 and Day 8) with an interval of 7 days to analyse intra-individual reliability. The signals obtained on Day 1 were used to analyse the inter-and intra-observer reliability of HRV parameters. The RR intervals, standard deviation of all RR intervals (SDNN), root mean square of the squared differences between adjacent normal RR intervals (RMSSD), the percentage of adjacent intervals over 50 ms (PNN50), and low (LF) and high (HF) frequencies were obtained. Frequency-domain variables were analysed using the autoregressive (AR) and fast Fourier transform (FFT) methods. Results: There were no intra-individuals difference in RR intervals between Day 1 and Day 8 (P>0.05). The intraclass correlation coefficient (ICC) ranged from 0.647 to 0.913, whereas the coefficient of variation (CV) was lower than 20% for all parameters, except PNN50 and LF/HF. The inter-and intra-observer reliability ranged from 0.915 to 0.996 and 0.990 to 0.993, respectively. In addition, the CV was lower than 20% (inter-observer) and 7% (intra-observer) to all HRV parameters. Conclusion: Indicators of reproducibility obtained in this study suggest that HRV can be used in adolescents; however, the analysis of HRV parameters should be performed by the same person.