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Updated: Feb 22, 2026
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Published on: July 1, 2015
Nocturnal heart rate variability in 1-year-old infants analyzed by using the Least Square Cosine Spectrum Method
Yuko Kochiya1, Akari Hirabayashi2, Yuhei Ichimaru2
1Tokyo Kasei University, 1-18-1 Kaga, Itabashi-ku, Tokyo, 173-8602, Japan. kochiya@tokyo-kasei.ac.jp.
Insights
Nocturnal heart rate variability in infants shows dynamic, rhythmic changes. Higher respiratory regularity (RA) correlates with decreased heart rate, suggesting increased parasympathetic activity and potential for infant health monitoring.
Area of Science:
- Pediatric Cardiology
- Infant Physiology
- Wearable Technology
Background:
- Nocturnal heart rate variability (HRV) in infants is dynamic.
- Understanding infant HRV is crucial for assessing autonomic nervous system function.
- Previous studies lacked detailed analysis of nocturnal HRV dynamics in infants.
Purpose of the Study:
- To evaluate the dynamic nature of nocturnal heart rate variability in 1-year-old infants.
- To introduce a novel method for quantifying respiratory-related heart rate rhythm regularity.
- To investigate the relationship between respiratory regularity and heart rate changes during sleep.
Main Methods:
- Utilized RR intervals from wearable heart rate sensors in six 1-year-old infants.
- Applied the Least Square Cosine Spectrum Method to analyze heartbeat time series.
- Introduced "RA (RA-COSPEC: Respiratory Area obtained by COSPEC)" to quantify respiratory-related heart rate rhythm regularity.
Main Results:
- Time-sequential RA values exhibited significant cyclic changes throughout the night with a mean cycle length of 70 ± 15 min.
- A shorter cycle length was observed compared to young adults in previous studies.
- Heart rate (HR) significantly decreased when RA exceeded a threshold of 3.
Conclusions:
- Infant heart rate rhythm regularity dynamically changes during the night.
- Higher RA values, associated with decreased HR, suggest increased parasympathetic activity.
- This analysis system offers a quantitative method for assessing nocturnal HRV dynamics in infants.
Background:
To evaluate the dynamic nature of nocturnal heart rate variability, RR intervals recorded with a wearable heart rate sensor were analyzed using the Least Square Cosine Spectrum Method.
Methods:
Six 1-year-old infants participated in the study. A wearable heart rate sensor was placed on their chest to measure RR intervals and 3-axis acceleration. Heartbeat time series were analyzed for every 30 s using the Least Square Cosine Spectrum Method, and an original parameter to quantify the regularity of respiratory-related heart rate rhythm was extracted and referred to as "RA (RA-COSPEC: Respiratory Area obtained by COSPEC)." The RA value is higher when a cosine curve is fitted to the original data series.
Results:
The time sequential changes of RA showed cyclic changes with significant rhythm during the night. The mean cycle length of RA was 70 ± 15 min, which is shorter than young adult's cycle in our previous study. At the threshold level of RA greater than 3, the HR was significantly decreased compared with the RA value less than 3.
Conclusions:
The regularity of heart rate rhythm showed dynamic changes during the night in 1-year-old infants. Significant decrease of HR at the time of higher RA suggests the increase of parasympathetic activity. We suspect that the higher RA reflects the regular respiratory pattern during the night. This analysis system may be useful for quantitative assessment of regularity and dynamic changes of nocturnal heart rate variability in infants.
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