A new study sheds light on the causes of sudden infant death syndrome. Does this mean a treatment could be on its way?
It's every new parent's worst nightmare: Sudden Infant Death Syndrome (SIDS), a condition that takes a newborn's life during sleep without warning. Although scientists have been able to identify some ways to reduce the risk of SIDS, its cause was still largely unknown—until now. A new study published in the journal Experimental Physiology may have found the key to why SIDS happens: a lack of the chemical serotonin in the brain.
New risk factors for SIDS
Researchers used rat pups to study the effects of serotonin on brief periods of breathing stoppages called "reflex apneas," which are believed to contribute to SIDS if they are severe. "We created reflex apneas in baby rats and tried to determine whether serotonin would shorten them—such an effect would be consistent with its tendency to stimulate regular breathing and arouse babies from sleep," study author James Leiter, M.D., of the Geisel School of Medicine at Dartmouth College in New Hampshire, tells Fit Pregnancy. To do this, they injected the chemical into the rodents' brain stems and timed the apneas to see if they got shorter—and they did, from 10 seconds to two. "We found that serotonin did shorten the reflex apneas, and it did so through a kind of receptor, the 5-HT3 receptor, that had not previously been studied in SIDS."
That sounds a bit complicated, but basically serotonin helps neurons in the brain communicate with each other through these receptors. In this way, it helps the brain know when to alert the baby to start breathing again after an apnea. "Many babies, including normal babies, have apneas, brief periods were they stop breathing, particularly during sleep, and serotonin seems to be important in restarting regular breathing," Dr. Leiter says. "It seems to be telling the neurons to do their job to stimulate breathing and wake the baby up."
Because many babies experience apneas, it's generally not something to worry about. But the problem for babies at risk for SIDS is that they might not have enough serotonin to restart their breathing. "It has been known for some time that many babies who die of SIDS have a relative deficiency of serotonin," Dr. Leiter says. "We believe that in addition, babies who are at risk for SIDS also have a greater tendency to have apneas and have more severe, longer lasting apneas. Babies at risk for SIDS have a two-fold problem: They are more prone to have apneas, and they have more difficulty terminating them."
Based on this study, it seems possible that a way to treat SIDS could be to test babies for serotonin deficiency, and supplement those who need it. "There may be tests that could be developed to identify babies at risk for SIDS, or there may be medicines that could be developed to prevent SIDS," Dr. Leiter says. But first, studies would need to be done to replicate the rat results in humans. "We are constantly on the look out for findings from animal studies that could be tested in human babies. If [this] finding is confirmed, then we may be able to use this information to develop tests or treatments to prevent SIDS."
What can parents do?
Until then, Dr. Leiter says there's not much that pregnant women can do to ensure their baby's brain chemistry develops properly in the womb. Smoking during pregnancy has been linked to higher SIDS rates, so definitely quit if you haven't already. "The best advice for women who are pregnant is to avoid those factors that increase the risk of SIDS, and create a safe sleeping environment when the baby is born," Dr. Leiter says.
The national Safe to Sleep campaign has a list of guidelines to follow for babies' sleep that helps lower the risk of SIDS. "The Safe to Sleep Campaign is working, the risk of SIDS is going down, but women should adhere to the guidelines to make them truly effective," Dr. Leiter says. These include:
- Don't use pillows, blankets, crib bumpers or stuffed animals in baby's bed.
- Use a firm mattress covered by a fitted sheet.
- Don't let anyone smoke around your baby.
- Place baby to sleep on his or her back.
- Don't sleep on a couch or chair with baby.
- Have baby sleep in your room, but not in your bed.
- Don't dress your baby too warmly, and keep the room temperature cool.
As this study suggests, infants who succumb to SIDS probably have factors in their brain that make them susceptible. But following these guidelines could reduce the chances of death in at-risk babies until scientists can more fully understand how to prevent it in the first place. "Every time we learn something new about how breathing, cardiac function and sleep are controlled in babies—even in baby rats—we have the chance to think about how these findings may be used to reduce the risk of SIDS in human infants," Dr. Leiter says. Hopefully, scientists will take that chance and find a cure soon.