Sudden unexpected death in infancy: a historical perspective.

Epidemiological, developmental and pathological research over the last 40 years has done much to unravel the enigma of sudden unexpected death in infancy (SUDI) and sudden infant death syndrome (SIDS) that has afflicted the human condition for millennia. Modifications in infant care practices based on the avoidance of risk factors identified from a consistent epidemiological profile across time and multiple locations have resulted in dramatic reductions in the incidence of SUDI and SIDS in particular. The definition of SIDS (or unexplained SUDI) has been continually refined allowing enhanced multidisciplinary research, results of which can be more reliably compared between investigators. These latter expanded definitions mandating death scene investigations, evaluation of the circumstances of death and more comprehensive autopsies including additional ancillary testing have illuminated the importance of life-threatening sleep environments. The triple-risk hypothesis for SIDS has been increasingly validated and formulates an inextricable relationship between an infant's state of development, underlying pathological vulnerability and an unsafe sleep environment for sudden infant death to occur. Today, the major risk factors for SUDI are maternal smoking and bed sharing, and the challenge is to implement effective strategies that will reduce the exposure to such risks as was done with prone sleeping position. The challenges ahead include development of clinical methods and/or laboratory testing that will accurately identify which infants are at particularly high risk of SIDS but also means by which their deaths can be prevented.