Altered arousal response in infants exposed to cigarette smoke.

AIMS: A failure of the arousal mechanism is a key feature in the apnoea theory for sudden infant death syndrome (SIDS). In infants studied at an age when the incidence of SIDS is highest, we evaluated whether in utero smoke exposed infants have altered arousal response to standardised auditory stimuli, and/or sleep pattern, as recorded on overnight complex sleep polysomnography. METHODS: A standardised sequence of audiology stimuli was applied binaurally to 20 in utero smoke and non-smoke exposed infants aged 8-12 weeks during a rapid eye movement (REM) and NREM epoch, in a controlled (temperature, position, pacifier use, noise) sleep environment. Infants were monitored for 10-12 hours using complex sleep polysomnography. RESULTS: Five infants exposed to in utero tobacco smoke did not have behavioural arousal response, whereas all non-smoke exposed infants aroused during NREM (p = 0.016). There was, however, no difference in REM sleep, and the groups did not differ in routine overnight complex sleep polysomnography parameters. CONCLUSION: At the age when the incidence of SIDS is at its peak, infants of smoking mothers are less rousable than those of non-smoking mothers in NREM sleep; this may partly explain why such infants are more at risk of SIDS.