Serotonin may be key to sudden infant deaths

Lack of the brain chemical
serotonin may be crucial to sudden infant death syndrome, new research finds.

Babies who died of SIDS had
significantly lower levels of serotonin – an important regulator of involuntary
functions such as breathing and heart rate – compared to babies who died of
other causes, the study found. This finding may eventually lead to a test that
could screen newborns to spot those most vulnerable to SIDS.

“This study is confirming that
SIDS is a serotonin problem, and we’re getting closer to the fundamental
mechanism behind SIDS,” said the study’s senior author, Dr. Hannah C.
Kinney, a neuropathologist at Children’s Hospital Boston and a professor of
pathology at Harvard Medical School.

“The goal is to develop a test
to identify which babies are at risk, and then to find a drug that might be
able to help them through the critical period. But these are long-term
goals,” she said.

Results of the study are published
in the 3 February issue of the Journal of the American Medical Association.

SIDS involves the sudden,
unexplained death of an infant under one year of age, according to background
information in the study. Although the rate of SIDS has decreased in the United
States  – largely as a result of a
national Back-to-Sleep campaign that encouraged parents to put babies to sleep
on their backs one out of every 2,000 American babies is still dying of SIDS,
the authors note.

Researchers have long suspected
that a lack of serotonin, an important neurotransmitter in the brain, may be a
factor in SIDS deaths. Neurotransmitters are chemicals that transmit messages
from one brain cell to another. Experts have theorised that a lack of serotonin
affects the way a baby responds to a loss of oxygen and a build-up of carbon
dioxide while sleeping. In babies with a normally functioning system, the lack
of oxygen would cause them to awaken and turn their head to get fresh oxygen.

In babies who die of SIDS, this
important protective mechanism is either underdeveloped or lacking, and they do
not awaken. That may be one reason why the Back-to-Sleep campaign was so
successful in reducing SIDS. By putting babies to sleep on their backs and
taking soft, fluffy bedding out of the crib, parents are taking away
environmental stressors that may contribute to SIDS, the researchers said.

In the current study, Kinney and
her colleagues measured levels of serotonin and trytophan hydroxylase (TPH2) in
35 babies who died from SIDS and in 12 babies who died of other, known causes.
TPH2 is an enzyme that helps make serotonin. In the group of babies who had
died of other causes, the researchers included infants who had experienced
oxygen deprivation near death to rule that factor out as a cause of lower
serotonin levels.

They found that serotonin levels
were 26 percent lower and TPH2 levels were 22 percent lower in babies who died
of SIDS compared to babies who died of other causes.

“This study is getting close
to the underlying mechanism,” said Dr. Raymond Pitetti, associate director
of emergency medicine at Children’s Hospital of Pittsburgh.

“The goal would be to develop
a screening test so we can identify someone who might need a monitor or to be
more closely watched,” he said.

In the meantime, he and Kinney
advised parents to continue to put their babies to sleep on their back, to
avoid soft bedding, to ensure adequate ventilation in the room where the baby
sleeps and maybe even add a ceiling fan to the room. Some research has suggested
that putting babies to bed with a pacifier in the mouth may help prevent SIDS,
too.

“The most
important thing for parents to know is that SIDS is a biological problem. It’s
a disease process, and right now, there’s no way to identify it in
advance,” said Kinney. That why it’s so important to take away any environmental
challenges, like soft bedding and sleeping on the stomach, she added.

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