Sudden Infant Death Syndrome from the Perspective of Arousal Deficiency

In Japan, it is mandatory to undertake efforts to prevent sudden infant death syndrome (SIDS), which continues to be responsible for a large portion of infant mortality. Etiological investigations of SIDS have been conducted independently in areas of epidemiology, physiology, and pathology, but mechanisms underlying the syndrome remain unknown. We conducted a comprehensive study which combined these disciplines. A theory of incomplete arousal has emerged for a pathophysiological hypothesis of SIDS, derived from reevaluation of a previously proposed apnea concept. As a consequence of this comprehensive study, we demonstrate that a tendency for arousal is reduced when an otherwise normal infant is subjected to epidemiological risk factors for SIDS and that a phenomenon of incomplete wakefulness exists in SIDS infants. Humans do not succumb solely because of incomplete arousal. According to the results of comprehensive examnation, the linking of pysiological and pathological data in single individuals, suggest that a change in neuronal plasticity of arousal pathways of the brain stem occurs, altering the basis for recognition and memory for a hypoxic state, thus triggering an infant’s untimely death.