According to a new study by researchers in the U.S. some babies who die from sudden infant death syndrome (SIDS) do so because of an abnormality in the serotonin system in their brains.
This abnormality say the researchers makes the babies more susceptible to SIDS.
Sudden infant death syndrome is the leading cause of post neonatal infant death in the United States and despite intensive research, the exact cause of SIDS remains rather elusive.
The researchers at the Children's Hospital in Boston say their discovery will confirm that SIDS is a disease process that's biologically based and not a mystery.
David Paterson, an instructor at the Harvard Medical School affiliated to the hospital, and one of the study's authors, suggests a complex combination of factors may be the cause of the abnormalities and they are unlikely to be exclusively genetic or environmental.
Paterson says the serotonin system is in an area of the brainstem called the medulla oblongata, and it is thought to regulate many vital body functions, including heart rate, breathing, blood pressure and temperature regulation.
An abnormality in this critical area might stop a baby from having a normal response when not getting enough air.
Should a baby be sleeping face down, he may be breathing in exhaled air and getting high levels of carbon dioxide; if the brain's serotonin system is working normally, it signals the baby to wake up and move his head to get fresh air.
Babies that die from SIDS, however, appear to not receive the right signals from the serotonin system to the rest of the body.
This new study supports previous research by the authors where serotonin-receptor defects were found in two other populations of SIDS babies.
Patterson says the confirmation of the abnormality in a third set of data, gives them confidence that the problem is in the serotonin system.
For the new research tissue samples from 31 babies who died of SIDS, were compared with that from 10 babies who died of other causes.
The researchers found that babies who died of SIDS had abnormalities in their serotonin receptor cells, had more serotonin-producing cells, but had too few serotonin-transporter cells, when compared to the control group of babies.
Paterson says now that they know there is a problem in the biology of the brainstem, something can hopefully be done about it.
Pediatric experts have praised the study but say the small numbers of babies involved and the under-representation of black infants, does mean the study has limitations.
They suggest a renewed focus on getting parents to put babies to sleep on their backs is needed.
It seems the majority of the infants included in this study were sleeping on their stomachs or sides.
Paterson advises that babies should sleep by themselves on a firm crib mattress with no soft bedding surrounding it; parents and others should not smoke around their babies and pregnant women should not smoke or drink alcohol.
The study is published in the Nov. 1 issue of the Journal of the American Medical Association.