Evolution and the sudden infant death syndrome (SIDS) : Part III: Infant arousal and parent-infant co-sleeping

This paper extends the evolutionary and developmental research model for SIDS presented in previous articles (McKenna 1990a, 1990b). Data from variety of fields were used to show why we should expect human infants to be physiologically responsive in a beneficial way to parental contact, one form of which is parent-infant co-sleeping. It was suggested that on-going sensory exchanges (touch, movement, smell, temperature, etc.) between co-sleeping parent-infant pairs might diminish the chances of an infantile cardiac-respiratory crisis (such as those suspected to occur in some SIDS cases).In this article we review recent epidemiological data and sleep research findings on SIDS to show how they relate to evolutionary and cross-cultural perspectives. Results of a preliminary study of the co-sleeping behavior of mother-infant pairs indicate that, with respect to sleep, arousal, and respiratory patterns, co-sleeping mother-infant pairs affect each other in potentially important ways. We suggest specifically that co-sleeping may shorten periods of consolidated sleep among young infants by causing them to arouse more frequently. Moreover, we suggest that partner-induced arousals might help the infant to confront sleep crises more competently. In the long run, these arousals might prevent the premature emergence of prolonged (adultlike) sleep bouts from which some infants have difficulty arousing-especially during a breathing pause or apnea.