SIDS researchers are reporting underlying brainstem abnormalities in infants dying suddenly and unexpectedly.
An Australian researcher is among those who also point to the need to detect and treat this underlying vulnerability early.
The findings, published in the December issue of Pediatrics, show infants who suffer sudden deaths, without explanation, have differences in brainstem chemistry that set them apart from infants dying of other causes.
These abnormalities impair brainstem circuits that help control breathing, heart rate, blood pressure and temperature control during sleep.
Researchers believe this prevents sleeping babies from rousing when they rebreathe too much carbon dioxide - due to inadequate ventilation, breathe too little oxygen or become overheated - from overbundling.
At the same time, epidemiologic studies have shown infants dying suddenly and unexpectedly are often found sleeping face down with their face in the pillow, or sleeping next to an adult in the bed - environments that have the potential to lead to smothering and death by asphyxia.
Dr Hannah Kinney at Boston Children's Hospital and the medical examiner's office in San Diego led the research which involved Australian SIDS researcher Dr Jhodie Duncan, who is now based in Melbourne at the Florey Institute of Neuroscience and Mental Health.
In the new study researchers asked if all these infants were truly normal.
They re-examined their data, reviewing the cases of 71 infants who died suddenly and unexpectedly, from autopsies at the San Diego County Medical Examiner's office from 1997 to 2008, and had brainstem samples available for analysis.
The investigators believe the findings confirm that sudden unexplained death in infants is associated with underlying vulnerabilities, and that not all infants who die in compromised sleep environments are normal.
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