Effects of sleep stage and age on short-term heart rate variability duringsleep in healthy infants and children

Study design: power spectrum analysis of heart rate variability (HRV) is a noninvasive technique that provides a quantitative assessment of cardiovasc ular neural control. Using this technique, we studied the autonomic nervous system changes induced by sleep in 14 healthy subjects: 7 infants (mean ag e, 9.40 +/- 2.32 months) and 7 children (mean age, 8.93 +/- 0.65 years) dur ing a standard all-night polysomnographic recording. Our primary aim was to assess the effect of sleep stage and age on short-term HRV during sleep in healthy infants and children. Power spectral density was estimated by auto regressive modeling over 250 consecutive R-R intervals. In this study, we m ainly considered two spectral components: the high-frequency (HF) component (0.15 to 0.40 Hz), which reflects parasympathetic cardiovascular modulatio n; and the low-frequency (LF) component (0.04 to 0.15 Hz), generally consid ered due to both parasympathetic and sympathetic modulation. Results: Heart rate was higher (p < 0.01 in all sleep stages) and total pow er ion er (p < 0.02) in infants than in children. HF power was higher in ch ildren than in infants (p < 0.05). In infants and children, the ratio betwe en LF and HF powers changed with the various sleep stages (p < 0.02 in infa nts; p < 0.01 in children): it decreased during deep sleep and increased du ring rapid eye movement sleep. However, it was invariably lower in children than in infants, Conclusion: These findings show that the sleep stage and age both significa ntly influence short-term HRV during sleep in healthy infants and children. Hence, to provide unbiased results, HRV studies investigating the effects of age on autonomic nervous system activity should segment sleep into the f ive stages. In addition, despite a relatively small study sample, our data confirm greater parasympathetic control during sleep in children than in in fants.