Identification of HRV Nonlinear Indices in Healthy Subjects with Age

Heart rate variability (HRV) is a complex phenomenon and beat-to-beat interval changes after every beat in healthy subjects. There are several studies on how HRV behavior varies with age. However, very few studies on participants less than one-year-old, and analysis through the Poincare plot have not been done yet. This study assessed the HRV as linear and nonlinear indices with different age groups using time domain, frequency domain, and nonlinear domain analysis. The Kruskal-Wallis test was used to assess the association of age with HRV indices. The heart rate showed linearly decrement with age, and SDNN first showed unexpected changes, then increased to 7–12 years old, then declined. Similar behavior was also seen by the RMSSD, NN50, and
$pNN50$
. VLF power varied greatly up to the age of one year, then steadily increased until 30, then decreased once again. Until 30, Lower Frequency, Higher Frequency, and total frequency power increased linearly before declining. Short-term and long-term variability showed peak values for 7-12-year-olds. The preadolescence (Group8) has a maximum heart rate variability indices increment. This study shows how the interpretation of HRV changes with age.