Effects of prematurity on arousal from sleep in the newborn infant

Abstract

The incidence of sudden infant death syndrome has been found to be consistently higher in preterm and low birth weight infants than in infants born at term. Failure to arouse from sleep is one possible mechanism for sudden infant death syndrome. This study compared the arousal responses to nasal air-jet stimulation in a longitudinal study between groups of healthy preterm and term infants. Preterm infants (n= 9) were born at 3135 wk gestation with normal birth weights for gestational age and studied on three occasions: a preterm study at 36 wk, at 23 wk post-term, and at 23 mo post-term. Term infants (n= 22) were born at 3742 wk and were studied at 23 wk and 23 mo post-term. Arousal thresholds were determined in both active sleep (AS) and quiet sleep (QS). In preterm infants, there was no state-related difference in arousal thresholds at either the 36 wk or 23 wk study; however, at 23 mo, arousal threshold was significantly greater in QS than AS (p“ 0.05). In contrast, in term infants, arousal thresholds were significantly elevated in QS compared with AS at both 23 wk and 23 mo (p“ 0.001). Arousal thresholds in AS were not different between the two groups of infants, with both groups of infants remaining readily arousable. However, in QS at 23 mo, arousal thresholds were significantly lower in the preterm infants (p“ 0.05). This study has demonstrated that arousability is altered by gestational and postnatal age. The lower arousability that characterizes QS in term infants regardless of age is not evident in preterm infants until 23 mo post-term age.© International Pediatrics Research Foundation, Inc. 2000. All Rights Reserved.