Effects of body position on sleep and arousal characteristics in infants

The prone sleeping position has been identified in world-wide epidemiological studies as a major risk factor for sudden infant death syndrome (SIDS). Public awareness campaigns throughout the western world have led to an over 50% reduction in postneonatal mortality and frequency of SIDS. This reduction in mortality has been mainly attributed to the avoidance of the prone sleep position. Various mechanisms have been postulated to explain the increased risk of SIDS associated with prone sleeping, among these, impairment of arousal from sleep. This paper reviews the effects of prone sleeping on infant sleep architecture, arousability from sleep and cardiorespiratory controls. Sleeping in the prone position has been shown to increase the amount of time spent sleeping, particularly time spent in quiet sleep (QS). Sleeping prone has also been demonstrated to be associated with a reduced responsiveness to a variety of arousal stimuli. Such impairment of arousal has been demonstrated to be associated with changes in control of autonomic cardiac function. During arousal, heart rate, blood pressure and breathing movements increase, while gross body movements occur to avoid the stimulus. Any impairment in arousability from sleep such as could occur when infants sleep in the prone position, could possibly contribute to the final pathway to SIDS.