Elsevier

The Journal of Pediatrics

Volume 132, Issue 2, February 1998, Pages 240-243
The Journal of Pediatrics

Auditory arousal thresholds are higher when infants sleep in the prone position,☆☆,,★★

https://doi.org/10.1016/S0022-3476(98)70438-XGet rights and content

Abstract

Objective: To evaluate the possibility that infants sleeping in the prone position have higher arousal thresholds to auditory challenges than when sleeping in the supine position.

Study design: Polygraphic recordings were performed for 1 night in 25 healthy infants with a median age of 9 weeks. The infants were exposed to white noises of increasing intensities while sleeping successively in the prone and supine positions, or vice versa. Arousal thresholds were defined by the auditory stimuli needed to induce polygraphic arousals.

Results: Three infants were excluded from the study because they awoke while their position was being changed. For the 22 infants included in the analysis, more intense auditory stimuli were needed to arouse the infants in the prone position than those in the supine body position (p = 0.011). Arousal thresholds were higher in the prone than in the supine position in 15 infants; unchanged in 4 infants; and lower in the prone position in 3 infants (p = 0.007).

Conclusions: Infants show higher arousal thresholds to auditory challenges when sleeping in the prone position than when sleeping in the supine position. The finding could be relevant to mechanisms concerned with the reported association between sudden deaths and the prone sleeping position in infants. (J Pediatr 1998;132:240-3).

Section snippets

Patients

Two groups of infants were studied between January 1995 and May 1996. All infants were healthy, born at term, and were admitted to join a sleep research program because of sleep-related behavior. The infants' auditory responses had been tested with audiometry after birth (Reactometer, Amplaid). None of the infants had a history of sleep problems or apnea. At the time of investigation, no signs of infection or neurologic problems were present, and none of the infants were receiving medications

Preliminary Study: Contralateral Ear Stimulation

No significant difference was seen in the frequency of polygraphic arousals or in the sound intensity needed to arouse the infants, whether their ears were free or occluded by the earplug. An auditory challenge of 50 dB(A) induced a polygraphic arousal in 12 of the 20 infants with both ears free from occlusion, and in 13 infants with the contralateral ear occluded.

Main Study: Determination of Arousal Thresholds

Of the 25 infants studied, 3 were excluded from the study because they awakened and remained awake for more than 30 minutes while

Discussion

In this study, healthy infants showed higher arousal thresholds to auditory challenges when they slept in the prone position than in the supine position. This finding could explain the reported association between infants' prone body position and a decreased tendency to arouse from sleep or to respond to environmental noises.1, 2

We cannot explain why body position influences arousal thresholds. Complex mechanisms relate auditory stimulations to arousals. The reticular formation of the brain

Acknowledgements

We thank Dr. E. Mitchell for his critical review of the manuscript.

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    From the Pediatric Sleep Unit, Erasmus Hospital and University Hospital for Children, Free University of Brussels, Belgium.

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    Supported by the Fondation Nationale de la Recherche Scientifique (grant No. 9.4524.87), and the Fondation Scientifique Universitaire Erasme.

    Reprint requests: A. Kahn, Pediatric Sleep Unit, University Hospital for Children Queen Fabiola, av. JJ Crocq 15, B-1020 Brussels, Belgium.

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    0022-3476/98/$5.00 + 0 9/21/83013

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