Why is a prone sleeping position dangerous for certain infants?

The prone (face down) sleeping position is known to be associated with a significantly increased risk of sudden and unexpected death in infancy (sudden infant death syndrome or SIDS), however, the reasons for this are unclear. Suggested mechanisms have involved suffocation from occlusion of the external airways by soft bedding/pillows or from flattening of the nose with backward displacement of the tongue, rebreathing of carbon dioxide, blunting of arousal responses with decreased cardiac responses to auditory stimulation, diaphragmatic splinting or fatigue, lowering of vasomotor tone with tachycardia, nasopharyngeal bacterial overgrowth, overheating, alteration of sleep patterns, compromise of cerebral blood flow and upper airway obstruction from distortion of nasal cartilages. Recent studies have, however, shown a significant reduction in substance P in the inferior portion of the olivo-cerebellar complex in SIDS infants which is crucial for the integration of motor and sensory information for the control of head and neck movement. This deficit may explain why some infants are not able to move their faces away from potentially dangerous sleeping environments.