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Updated: Sep 27, 2026
Preterm EEG: A Multimodal Neurophysiological Protocol
Published on: February 18, 2012
Effect of position on sleep, heart rate variability, and QT interval in preterm infants at 1 and 3 months' corrected
Ronald L Ariagno1, Majid Mirmiran, Marian M Adams
1Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA. rla@stanford.edu
Insights
Prone sleeping in infants did not improve sleep but increased risks for SIDS by prolonging QT intervals and reducing heart rate variability (HRV). The "Back to Sleep" campaign is crucial for infant safety.
Area of Science:
- Neonatal physiology
- Sleep medicine
- Cardiology
Background:
- The prone sleeping position is linked to Sudden Infant Death Syndrome (SIDS).
- The "Back to Sleep" campaign significantly reduced SIDS rates.
- The underlying mechanisms of sleep position effects on infant physiology require further investigation.
Purpose of the Study:
- To test the hypothesis that prone sleeping alters sleep, arousal, heart rate variability (HRV), and electrocardiogram (ECG) QT intervals.
- To investigate the physiological impact of sleeping position on premature infants.
Main Methods:
- Longitudinal study of 16 premature infants at 1 and 3 months corrected age.
- Videosomnography and ECG recordings during naps in both supine and prone positions.
- Analysis of sleep stages, HRV (time and frequency domains), and ECG intervals (QT, JT).
Main Results:
- No significant differences in total sleep time or quiet sleep (QS) percentage between positions.
- Prone sleeping showed significantly lower active sleep (AS) percentage and fewer sleep transitions at 1 month corrected age.
- Prone sleeping was associated with reduced HRV during QS and significantly longer QT and JT intervals at 1 month corrected age.
Conclusions:
- Prone sleeping did not enhance sleep but potentially increased SIDS vulnerability in premature infants.
- Findings support the "Back to Sleep" campaign for both term and preterm infants.
- Physiological changes in prone position, including prolonged QT intervals and reduced HRV, may explain SIDS risk.
Objective:
Prone sleeping position has a strong link to sudden infant death syndrome (SIDS), and the "Back to Sleep" campaign has played an important role in reducing SIDS. We tested the hypothesis that the mechanism of the sleep position effect is based on changes in sleep, arousal, heart rate variability (HRV), and the QT interval of the electrocardiogram.
Study Design:
We studied 16 premature infants longitudinally, at 1 and 3 months' corrected age. Videosomnography recordings were made during the infants' normal daytime naps. Each infant was recorded in both supine and prone positions. The recordings were analyzed in 30-second epochs, which were classified as awake, active sleep (AS), quiet sleep (QS), or indeterminate sleep. Electrocardiogram data were sampled with an accuracy of 1 millisecond. Time domain analysis of HRV was measured by standard deviation of all R-R intervals and by the square root of the mean of the sum of the squares of the differences between adjacent R-R intervals. Frequency domain analysis was done for low frequency (0.04-0.14 Hz) and high frequency (0.15-0.5 Hz) HRV. We measured QT, JT, and R-R intervals during AS and QS for each position.
Results:
We found no significant differences between supine and prone position, either in total sleep time or in percentage of QS. Percentage of AS was significantly lower in the supine position, but only at 1 month corrected age. The incidence of short, spontaneous, sleep transitions was significantly higher in supine, also only at 1 month corrected age. Time domain analysis of HRV showed a significantly lower variability in prone, but only during QS. Frequency domain analysis of HRV showed no differences between the 2 sleeping positions. Both QT and JT intervals were significantly longer in prone during QS, but only at 1 month corrected age.
Conclusions:
Despite the commonly held belief, prone position did not substantially increase total sleep at these ages. On the other hand, prone sleeping decreased the number of sleep transitions at 1 month corrected age, increased QT and JT intervals, and reduced HRV, thereby potentially increasing the vulnerability for SIDS. This study supports "Back to Sleep" as the position of choice not only for term but also for preterm infants after discharge home.
