Research overview

Multiple causes of Sudden Infant Death (SID) point to more than one pathway for prevention. Scientists are exploring many factors to determine the possible underlying causes for infants who die of SIDS. The physiological variables being examined include breathing and sleep patterns, the brain, the heart, development and function of the nervous system, and body chemical changes. Environmental factors, death scene investigations and autopsy findings are also considered.

The MN Sudden Infant Death (SID) Center at Children’s Minnesota stays current on these research findings and also partners with state and other agencies to track and prevent sudden infant deaths statewide.

Studies continue to support the view that SID deaths occur when multiple risks are present at the same time. This is referred to as the Triple-Risk Model:

Image from F Trachtenberg, et al. Risk factor changes for Sudden Infant Death Syndrome after initiation of back-to-sleep campaign. Pediatrics 2012; 129:630-638.

  • Vulnerable infant. The first key element of the triple-risk model suggests an infant with an underlying defect or abnormality, which makes the baby vulnerable. In this model, certain pathophysiological 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. Two important studies described below examine the biological vulnerabilities of brain abnormalities and low levels of serotonin.
  • Critical development period. The second element in the triple-risk model refers to the infant’s first six 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.
  • Exogenous stressor. The third element of this model involves outside stressors. These may include environmental factors (e.g., exposure to tobacco smoke, overheating, or tummy 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. By themselves, these stressors do not cause infant deaths, but in a vulnerable infant, they may have an influence in that infants chances of survival. 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.

Brain abnormalities in SIDS infants and low serotonin levels.

With respect to physiological vulnerabilities of SIDS infants, a team of researchers funded by the National Institute of Child Health and Human Development (NICHD) has discovered that infants who die of SIDS may have abnormalities in several parts of the brainstem. This finding builds on the results of an earlier study that identified abnormalities in the region of the brain known as the arcuate nucleus in babies who died of SIDS.

In the NICHD study, SIDS infants were found to have decreased binding of serotonin in the nucleus raphe obscurus, a brain structure linked to the arcuate nucleus, as well as four other brain regions. These areas of the brain are thought to play an important role in regulating breathing, heart beat, body temperature, and arousal. Another more recent study found SIDS to be linked to low levels of serotonin.

Statewide partnerships track and prevent infant death

Further reading


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