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Heart rate biorhythm changes during the first three months of life
Insights
Newborn heart rate (HR) exhibits an initial 3-hour ultradian rhythm. This circadian rhythm emerges within 15-30 days, indicating developmental maturity in neonates.
Area of Science:
- Neonatal physiology
- Chronobiology
- Cardiovascular development
Background:
- Heart rate (HR) regulation in newborns is crucial for assessing physiological maturity.
- Understanding temporal patterns in neonatal HR can provide insights into developmental trajectories.
Purpose of the Study:
- To investigate the presence of circadian and ultradian rhythms in heart rate of healthy newborns.
- To determine how these rhythms change with postnatal age and indicate developmental maturity.
Main Methods:
- Continuous 24-hour heart rate monitoring at 30-minute intervals in newborns aged 1-90 days.
- Data analyzed across six postnatal age groups (days 1, 7, 15, 30, 60, 90).
- Cosinor analysis applied to identify ultradian and circadian rhythms in heart rate patterns.
Main Results:
- A 3-hour ultradian rhythm was identified in newborns on days 1, 7, and 30 (p < 0.01).
- A 12-hour ultradian rhythm was observed in 90-day-old newborns (p < 0.01).
- Circadian rhythms were confirmed in newborns aged 30, 60, and 90 days (p < 0.05).
Conclusions:
- Newborns possess an intrinsic 3-hour ultradian heart rate rhythm at birth.
- The development of a circadian rhythm in heart rate occurs between 15 and 30 days of postnatal life.
- These findings highlight the maturation of cardiovascular regulation in early infancy.
Unlabelled:
Heart rate (HR) was recorded in healthy full-term newborns aged 1-90 days. The aim of this study was to study the existence of circadian and/or ultradian rhythms in HR to determine maturity. HR was recorded during 24 h, at 30-min intervals, at different postnatal ages. Six-groups were investigated: day 1 (group 1); day 7 (group 7); day 15 (group 15); day 30 (group 30); day 60 (group 60), and day 90 (group 90). The chronograms for HR showed peaks and nadirs along the 24-hour periods, and the cosinor analysis proved the existence of 3-hour ultradian rhythm in groups 1, 7 and 30, and a 12-hour ultradian rhythm in group 90 (p < 0.01 in all cases). The same type of analysis confirmed the existence of a circadian rhythm in group 30. Similar results were obtained for groups 60 and 90 (p < 0.05).
In Conclusion:
at birth, newborns have an endogenous ultradian period of 3 h. A circadian rhythm appears within 15-30 days of postnatal life.