Failure to Arouse from Sleep May Play a Role in Sudden Infant Death Syndrome (sids).1,2 an In- Sufficient Propensity to Arouse Could Lower

FAILURE TO AROUSE FROM SLEEP MAY PLAY A ROLE IN SUDDEN INFANT DEATH SYNDROME (SIDS).1,2 AN INSUFFICIENT PROPENSITY TO AROUSE COULD LOWER the chance of infants surviving when they are exposed to noxious conditions during sleep.3 Compared with matched control infants, infants who eventually died of SIDS have been shown to have fewer body movements and awakenings from sleep, especially by the end of the night when most deaths occur.4,5 Arousals reflect a progressive activation of various structures, from subcortical to cortical areas.6-8 Autonomic and brainstem arousals can occur without changes in cortical activity.9,10 We have previously showed that future SIDS victims have more subcortical activations and fewer cortical arousals than control infants, suggesting an incomplete arousal process in infants who eventually die of SIDS.11 The prone sleeping position has been identified in worldwide epidemiologic studies as a major risk factor for SIDS.12-14 Public awareness campaigns throughout the Western world have led to an over 50% reduction in postneonatal mortality and the frequency of SIDS.15 This reduction in mortality has been mainly attributed to the avoidance of the prone sleep position. Various mechanisms have been postulated to explain the association of prone sleeping and SIDS. These include accidental suffocation,16 oropharyngeal obstruction due to nasal obstruction,17 posterior displacement of the mandible,18 increased upper airway resistance,19 inhibitory inputs from atrial stretch receptors,20 compromise of cerebral blood flow during cervical hyperextension,21 suffocation due to rebreathing expired air,22,23 overheating,24 development of nasal bacterial toxins,25 and impairment of autonomic function.26 A defective arousal response from sleep has also been postulated as a likely mechanism to explain why sleeping prone increases the risk of SIDS.27 Compared with sleeping in the supine position, sleeping in the prone position is associated in healthy infants with a significant decrease in the frequency and duration of spontaneous arousals during both rapid eye movement (REM) and non-REM (NREM) sleep.27-29 Sleeping prone has also been demonstrated to be associated with reduced responsiveness to a variety of internal or external arousal stimuli.27,29-31 The present study was undertaken to evaluate whether prone sleep position in healthy infants impairs arousal process, as has been previously seen in SIDS infants.