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Time of night effects on heart rate variation in normal neonates
1Brain Research Institute, UCLA School of Medicine 90024-1761.
Insights
Newborn heart rate variation changes throughout the night, especially during quiet sleep. These circadian patterns in heart rate variability are present in early infancy.
Area of Science:
- Neonatal physiology
- Sleep science
- Cardiovascular regulation
Background:
- Circadian rhythms manifest early in human infancy, with observable patterns within days of birth.
- Heart rate variation (HRV) is a key indicator of autonomic nervous system activity and developmental status in neonates.
Purpose of the Study:
- To investigate temporal variations in heart rate variability across different sleep-wake states in newborn infants over a 12-hour night.
- To determine if specific frequency bands of HRV exhibit consistent changes throughout the night in neonates.
- To examine the interplay between sleep state, time of night, and HRV patterns in early infancy.
Main Methods:
- Acquisition of 12-hour polysomnographic recordings (EEG, ECG, EOG, EMG, respiration, CO2) from 25 healthy full-term neonates (2-7 days old).
- Epoch identification into quiet sleep, rapid eye movement (REM) sleep, and waking states.
- Quantification of three types of heart rate variation within distinct frequency bands for each sleep-wake state and 4-hour time period.
Main Results:
- Heart rate variation in specific frequency bands decreased from evening to late night across particular sleep-wake states.
- HRV at the respiratory frequency showed a time-of-night effect exclusively during quiet sleep.
- Respiratory sinus arrhythmia, while enhanced in quiet sleep during the evening, lost this state-specific advantage later in the night.
Conclusions:
- Time-of-night influences on HRV are state-dependent in neonates, not uniformly affecting all physiological states.
- The tendency for enhanced respiratory sinus arrhythmia during quiet sleep, observed later in infancy, is present in neonates but primarily expressed in the evening.
- Heart rate variation during the waking state demonstrates minimal responsiveness to nocturnal circadian influences in newborns.
Abstract:
Circadian patterns have been observed in infants as early as the first few postnatal days. We hypothesized that, in each sleep-waking state, heart rate variation in several distinct frequency bands would show consistent variations across a night in newborn infants. Twelve-hour night-time recordings of EEG, ECG, EOG, digastric EMG, respiratory movements, and CO2 were obtained from 25 normal full-term infants at 2-7 days postnatal age. The extents of three types of heart rate variation were determined for all epochs identified as quiet sleep, rapid eye movement (REM) sleep, and waking during each 4-hr period of the night. In particular states, the extent of all three types of heart rate variation decreased from the evening (7-11pm) to the late night (11pm-3am). Heart rate variation at the respiratory frequency showed such a time-of-night effect in quiet sleep only, resulting in a significant sleep state effect on respiratory sinus arrhythmia during the evening that disappeared later in the night. Previous studies have indicated that respiratory sinus arrhythmia is enhanced during quiet sleep, relative to other states, after 3 mo of age; the present findings suggest that the tendency for enhancement during quiet sleep is present even in the neonate, although this tendency is only expressed during the evening. Results indicate that time-of-night effects on heart rate variation are not constant across physiological states in neonates, and heart rate variation during the waking state is particularly unresponsive to these time-of-night influences.