Definition (Pediatrics 2011;128:e1341; Pediatr Rev 2007;28:209)
• Cause assigned to unexplained death of infant <1 yo after thorough eval including scene investigation, autopsy, and review of clinical history. Infant usually previously healthy
• Comprises majority of SUID (sudden unexpected infant death), which is term for all such deaths, whether cause identified or not
Epidemiology
• 2,327 infants in 2006 in US: 3:2 – 
:
, Black and American-Indian infant rates double that of white infants. Asian and Hispanic infants rate half of white infants
• Rate ↓ from 1.2 deaths per 1,000 live births in 1992 to 0.57 in 2001, stable since then. AAP issued recs on supine sleeping in 1992, “Back to Sleep” education campaign began in 1994. Changes since 1999 may be related to reclassification of other causes of SUID
• Similarly, prevalence of supine sleep positioning stable since 2001 at 75%
• Third leading cause of death in infancy, top cause of death in 1–12 mo-old age group
Risk Factors
• Prone and side sleeping positions (↑ risk of re-breathing expired gasses), soft bedding, overheating. Risk higher in side sleeping than in prone position
• Maternal smoking during pregnancy and environmental tobacco smoke
• Inadequate prenatal care, young maternal age, prematurity or low birth weight
• Family with one SIDS death has 2–6% risk of a second SIDS death
Pathophysiology: Proposed Mechanisms
• Convergence of exogenous stressor (i.e., prone position), critical period of development (i.e., immature cardio-respiratory/arousal systems), & vulnerable infant (i.e., LBW) lead to progressive asphyxia, bradycardia, HoTN, met acidosis, ineffectual gasping, and death
• Re-breathing theory: Prone infants trap exhaled CO2 around face, ↓ arousal. Some SIDS infants w/ brainstem w/ 5HT-R abn at ventral medulla; ↓ arousal resp to hypercarbia & hypoxia
• In utero nicotine exposure alters expression of nicotinic acetylcholine receptor in brainstem areas that control autonomic function, depresses recovery from hypoxia, and impairs arousal patterns
• Some SIDS infants w/ polymorphisms in 5HT transporter gene w/ ↓ [5HT] at synapse
• Other genes related to QT prolongation and autonomic nervous system development
Differential Diagnosis
• Sepsis, PNA, cardiomyopathy, congenital heart dz, arrhythmia, prolonged QT, accidental or non-accidental trauma, suffocation, and inherited metabolic disorders
Risk Reduction
• Supine sleep position at all times (remind 2° caregivers)
• Firm crib mattress covered w/ single fitted sheet; avoid blankets but if used, should be tucked in on 3 sides, not covering the face/head
• Breast-feeding (may reduce risk of SIDS by 50%)
• Avoidance of tobacco, smoke, alcohol, and illicit drug exposure
• Pacifier use confers protection (50–60% ↓ risk). Begin after breastfeeding established
• Room sharing without bed sharing (can reduce risk of SIDS by 50%). No evidence that in-bed co-sleepers reduce risk of SIDS & are not recommended by AAP. Avoid co-bedding of twins and multiples
• Routine immunization (may reduce risk of SIDS by 50%)
• Avoid overheating. (Risk of SIDS may be reduced in well-ventilated rooms, possibly with use of fan)