Objective: Impairment of the arousal process from sleep is thought to be involved in the pathogenesis of sudden infant death syndrome (SIDS). We hypothesized that a greater propensity for cortical arousal in the prone position may, in a normal infant, be a protective mechanism to promote complete arousal in a vulnerable sleeping position, a protection that is absent in SIDS victims. We aimed to examine the arousal process in a group of infants exposed to maternal smoking, who are thus at higher risk for SIDS.
Design: Twelve healthy, full-term infants born to smoking mothers were studied using daytime polysomnography at 2 to 4 weeks, 2 to 3 months and 5 to 6 months postnatal age. Data were compared with 13 healthy infants born to nonsmoking mothers. Arousal was induced by pulsatile air-jet stimulation to the nostrils during active and quiet sleep, in both supine and prone positions. For each stimulus, physiologic and electroencephalogram changes were visually assessed and arousal responses were classified as sub-cortical activation or cortical arousal.
Results: In smoke-exposed infants, the progression from sub-cortical activation to cortical arousal was depressed at 2 to 4 weeks and 5 to 6 months. There was no effect of maternal smoking observed at 2 to 3 months; however, a significant dose-dependent relationship between cortical activation proportions and urinary cotinine levels was present in both supine and prone positions.
Conclusion: We have shown that maternal smoking is associated with impaired arousal processes to trigeminal stimulation that may increase the risk for SIDS. This further highlights the importance of public education of the risks of maternal smoking.
Keywords: Smoking, SIDS, arousal, sleep