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Development of linear and non-linear properties of heart rate control during quiet and active sleep in healthy
1Institute of Physiology, Humboldt-University of Berlin, University Hospital Charité.
Insights
Infant heart rate control shows distinct developmental periods. Analysis reveals adaptation in the first month, followed by clearer patterns until six months, utilizing linear and non-linear methods.
Area of Science:
- Cardiology
- Developmental Biology
- Physiology
Background:
- Heart rate variability (HRV) is crucial for infant health.
- Understanding autonomic nervous system development in newborns is essential.
- Previous studies often used linear methods, potentially missing complex dynamics.
Purpose of the Study:
- To analyze the development of instantaneous heart rate (IHR) control in infants.
- To differentiate developmental patterns during quiet and active sleep.
- To apply both linear and non-linear methods for a comprehensive analysis.
Main Methods:
- Studied ten healthy, term newborns during their first six months.
- Calculated low frequency (LF) and high frequency (HF) power spectra from IHR.
- Determined the largest Lyapunov exponent (LLE) to assess non-linear dynamics, validated with surrogate data tests.
Main Results:
- Infant heart rate control exhibited irregular patterns in the first month, with a notable dip in LLE on day 21.
- High frequency (HF) power significantly increased between 2-6 months during quiet sleep.
- No significant correlations were found for LF and LLE in either sleep state after the first month.
Conclusions:
- Infant heart rate regulation follows two main developmental phases: initial adaptation (first 4 weeks) and a period of clearer development (up to 6 months).
- Non-linear analysis (LLE) confirms the complex, evolving nature of infant autonomic control.
- Findings highlight the importance of considering both linear and non-linear dynamics in infant cardiovascular research.
Abstract:
In this study it is analyzed by linear and non-linear methods, how the control of instantaneous heart rate (IHR) develops in infants in quiet and active sleep. Ten healthy and term newborns were studied during their first half year of life. Low (LF) and high frequency power (HF) of the spectrum, and the largest Lyapunov exponent (LLE) were calculated from IHR. By means of the surrogate-data-test, significance of LLE with respect to linear correlated gaussian noise was verified. Significant differences were determined between the original and the surrogate data sets (p < 0.001) assuming non-linear properties. LF, HF, LLE have irregular developmental patterns during the first month, whereby LLE has a distinct low value on the 21st day. HF significantly increases between the second and sixth month in quiet sleep, whereas for LF and LLE no significant correlations were found, neither for quiet nor active sleep. Using linear and non-linear methods, the study shows that the system controlling heart rate pass through mainly two different developmental periods: a period of adaptation in the first four weeks, where parameters distinctly vary, followed by a period with clear developmental courses, lasting till the sixth month.