The Triple Risk Model
Pathology studies of SIDS infants support the view that these infants possess underlying vulnerabilities that put them at risk for sudden death, a concept advanced by the triple-risk model in describing the sequence of events leading to the death of an infant. A number of scientists are currently applying this model in their search for a cause(s) of SIDS.
- Vulnerable Infant. The first key element of the triple-risk model depicts an infant with an underlying defect or abnormality, which makes the baby vulnerable. In this model, certain athophysiological factors (e.g., defects in the parts of the brain that control respiration or heart rate, and that occur during early life) explain vulnerability to sudden infant death.
- Critical Developmental Period. The second element in the triple-risk model refers to the infant's first 6 months of life. During this critical developmental period, rapid growth phases occur and changes in homeostatic controls take place. These changes may be evident (e.g., sleeping and waking patterns), or they may be more subtle (e.g., variations in breathing, heart rate, blood pressure, and body temperature). It may be that some of these changes may temporarily or periodically destabilize the infant's internal systems.
- Outside Stressor(s). The third element of this model involves outside stressors. These may include environmental factors (e.g., exposure to tobacco smoke, overheating, or prone sleep position) or an upper respiratory infection that most babies can experience and survive, but that an already-vulnerable infant may not be able to overcome. In and of themselves, these stressors do not cause infant deaths, but in a vulnerable infant, "may tip the balance against an infant's chances of survival" (Filiano and Kinney, 1994). According to this model, all three elements must interact for a sudden infant death to occur—the baby's vulnerability is undetected until the infant enters the critical developmental period and is exposed to an outside stressor or stressors.