Relationship between frequency spectrum of heart rate variability and autonomic nervous activities during sleep in newborns

Abstract Introduction We analyzed the frequency spectrum of two neonatal sleep stages, namely active sleepand quietsleep, and the relationship between these sleep stages and autonomic nervous activity in 74 newborns and 16 adults as a comparison. Method Active and quietsleep were differentiated by electroencephalogram (EEG) patterns, eye movements, and respiratory wave patterns; autonomic activity was analyzed using the RR intervalof simultaneously recorded electrocardiogram (ECG) signals. Power values (LFa, absolute low frequency; HFa, absolute high frequency), LFa/HFa ratio, and the values of LFn (normalized low frequency) and HFn (normalized high frequency) were obtained. Synchronicity between the power value of HFa and the LFa/HFa ratio during active and quietsleep was also examined by a new method of chronological demonstration of the power values of HFa and LFa/HFa. Results We found that LFa, HFa and the LFa/HFa ratio during active sleepwere significantly higher than those during quietsleep in newborns; in adults, on the other hand, the LFa/HFa ratio during rapid eye movement (REM) sleep, considered as active sleep, was significantly higher than that during non-REM sleep, considered as quietsleep, and HFa values during REM sleep were significantly lower than those during non-REM sleep. LFn during quietsleep in newborns was significantly lower than that during active sleep. Conversely, HFn during quietsleep was significantly higher than that during active sleep. Analysis of the four classes of gestational age groups at birth indicated that autonomic nervous activity in a few preterm newborns did not reach the level seen in full-term newborns. Furthermore, the power value of HFa and the LFa/HFa ratio exhibited reverse synchronicity. Conclusion These results indicate that the autonomic patterns in active and quietsleep of newborns are different from those in REM and non-REM sleep of adults and may be develop to the autonomic patterns in adults, and that parasympathetic activity is dominant during quietsleep as compared to active sleepfrom the results of LFn and HFn in newborns. In addition, in some preterm infants, delayed development of the autonomic nervous system can be determined by classifying the autonomic nervous activity pattern of sleep stages.