Serotonin May Be the Key to SIDS12/08/10
WEDNESDAY, Dec. 8 (HealthDay News) -- Sudden infant death
syndrome, or SIDS, has for years had a reputation as a mysterious
and terrifying killer of newborns.
But medical researchers now think they have cracked the secret
of what causes babies to die of SIDS, an advance that could save
hundreds of lives each year.
Doctors have found that babies who die of SIDS tend to have
significantly lower amounts of serotonin than babies who die of
other causes. Serotonin is a hormonal neurotransmitter closely
linked to many of the body's vital functions, including the
A lack of serotonin is suspected to hamper a sleeping baby's
ability to wake up when its safety is threatened by a lack of
oxygen or some other health hazard, said Dr. Rachel Y. Moon, a
pediatrician, SIDS researcher and associate chief of the division
of general pediatrics and community health at the Goldberg Center
for Community Pediatric Health at Children's National Medical
Center in Washington, D.C.
"We think a lot of it has to do with arousal, and how babies can wake up when they are asleep," Moon said. "If you have a baby who gets into a compromised situation and they are becoming hypoxic, there are some babies who are sleeping so deeply or have an arousal defect that they can't wake up."
SIDS is the leading cause of death for babies between 1 month
and 1 year of age, according to the U.S. National Institutes of
Health. Most SIDS deaths occur between the ages of 2 months and 4
months, and more than 2,200 U.S. infants die of SIDS every
These deaths are sudden and unexplained, even after doctors
perform an autopsy and review the infants' health. Since most of
these deaths happen when the babies are sleeping, SIDS is known to
many as "crib death."
Researchers believe that some sort of birth defect leads to the
serotonin deficit in some babies, said Laura Reno, vice president
of public affairs for First Candle, a nonprofit organization
dedicated to the study and prevention of SIDS.
Some of the most recent research came from work headed by Dr.
Hannah C. Kinney, a neuropathologist at Children's Hospital Boston
and a professor of pathology at Harvard Medical School. Kinney, a
leading SIDS researcher, and her colleagues found that serotonin
levels of 35 babies who died of SIDS were 26 percent lower than
those of babies who died of known causes. The SIDS infants also had
22 percent lower levels of tryptophan hydroxylase, an enzyme that
helps make serotonin.
Serotonin is suspected to be crucial to a baby's arousal system,
which Reno likened to an "alarm" that wakes a baby up when the
infant's health is compromised.
"In these babies, the alarm doesn't sound," Reno said. "They continue to sleep even if there is a challenge in their environment, which then causes them to die."
Environmental hazards that could lead to a SIDS death, Reno
- Belly sleeping. Infants allowed to sleep on their stomachs end
up rebreathing their own exhaled air rather than fresh air. "They
are taking in carbon dioxide instead of oxygen," which creates an
oxygen deficiency that can result in death, Reno said.
- Overheating. Babies dressed too warmly or swaddled in thick
blankets can become too warm for their own health. "These babies
get too heated and, again, the alarm doesn't sound," she said.
- Too much soft and fluffy bedding and pillows in a crib also can
cause a baby to smother. Babies who sleep in the same bed as their
parents also are more likely to die of SIDS, Reno said.
- Smoking. Cigarette smoke robs sleeping babies of needed oxygen.
Secondhand smoke, she said, is "really dangerous for these
The next step in research would be to find a way to identify
babies who suffer from a natural lack of serotonin. "That would be
the goal, because then we would be better able to target
messaging," Moon said.
In the meantime, parents are urged to follow the recommendations
that doctors have been issuing for years to limit SIDS deaths:
- Always place babies on their backs to sleep. Since the American
Academy of Pediatrics issued this recommendation in 1992, SIDS
deaths have dropped by more than half, according to the Nemours
- Place babies on a firm sleeping surface with a tightly fitted
sheet. Don't allow a baby to sleep on a pillow, quilt or other soft
- Dress babies in light clothing for sleep, and keep the room at
a temperature that adults would find comfortable.
- Give babies a pacifier when putting them down to sleep. Studies
have found that babies who use pacifiers are less likely to die of
SIDS. "We think it may change the baby's arousal threshold, or the
way the baby breathes," Moon said.
These are guidelines that parents should follow regardless of
whether they believe their child may suffer from a serotonin
deficiency, Moon added.
"Babies do suffocate," she said. "Babies do get trapped between mattresses and other things. So these safe-sleep recommendations will help protect against those things as well."
The U.S. National Institute of Child Health and Human
Development has more on
For more on SIDS, read about
one mother's experience.
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