Leading cause of infant death beyond the neonatal period.
Incidence roughly 1 in 2000 infants.
Peak incidence between 1 and 3 months of age, although events may occur up to 12 months of age.
Risk factors include exposure to tobacco smoke (antenatally and postnatally); prone and side sleeping; bed-sharing during sleep; a sleep environment that includes soft mattress and/or sleeping surface (including sofa or armchair), and placement of soft sleep bedding; over-bundling/over-heating; prematurity; exposure to alcohol and illicit drugs (antenatally and postnatally); and viral infection. Several risk factors may co-exist in any given patient.
Protective factors include use of a dummy during sleep, immunisation, and breastfeeding.
Careful evaluation of death by trained forensics teams is necessary to rule out other causes of death, including suffocation, asphyxia, entrapment, infection, ingestions, metabolic diseases, arrhythmia-associated cardiac channelopathies, and trauma (accidental or non-accidental).
The term 'sudden infant death syndrome' (SIDS) was first used, and an early definition described, at the 2nd International Conference on the Causes of Sudden Death in Infants in 1969.  In 1991, the definition was modified by a panel convened by the National Institute of Child Health and Human Development. The panel defined SIDS as "The sudden death of an infant under 1 year of age, which remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and a review of the clinical history".  This remains the widely accepted definition, and is the preferred definition of the American Academy of Pediatrics Task Force on Sudden Infant Death Syndrome.  Although some have advocated the addition of the criterion that onset of the fatal event seems to be associated with sleep,   this criterion remains controversial.
Professor of Pediatrics
University of Virginia School of Medicine
RYM receives grant funding from the National Institutes of Health, receives honoraria for speaking at various conferences, and is a board member of the International Society for the Study and Prevention of Perinatal and Infant Death. She has provided expert testimony in a case of an infant who died suddenly and unexpectedly.
Dr Rachel Y. Moon would like to gratefully acknowledge Dr John W. Berkenbosch, a previous contributor to this topic. JWB declares that he has no competing interests.
Professor of Infant Health & Developmental Physiology
FSID Research Unit
Institute of Child Life and Health
St Michaels Hospital
PF is an author of a number of references cited in this topic.
Professor and Vice-Chair
Department of Pediatrics
UMDNJ-Robert Wood Johnson Medical School
TH declares that he has no competing interests.
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