Most of the seemingly healthy babies who die suddenly in their sleep may have undetected brain abnormalities, according to research from Boston Children’s Hospital that is being published Monday.
The scientists observed defects in the breathing-control region in the brains of babies whose deaths were attributed to sudden infant death syndrome, or SIDS. The abnormalities were present whether infants had been put to bed in a safe sleeping position — on their backs — or in unsafe sleeping positions on their bellies, face-down, or surrounded by pillows and heavy blankets.
That finding, said Dr. Hannah Kinney, a neuropathologist at Children’s who coauthored the study, could provide some comfort to parents who have gone through the heartbreak of losing a baby unexpectedly. “There may be a biological explanation behind all this, which can relieve guilt and lessen grief.”
But Kinney added, “It is still important for all babies to be put to bed in a safe sleep position since we know that has led to a decline in deaths.”
About 4,000 American babies die suddenly of no known cause before their first birthday, according to the federal Centers for Disease Control and Prevention; half of these deaths are due to SIDS, when babies suffocate accidentally after getting trapped in bedding or stop breathing for an unexplainable reason.
Two years ago, the American Academy of Pediatrics recommended an expanded array of measures parents should take to prevent SIDS deaths — beyond putting babies to sleep on their backs — including sharing a room but not a bed with baby, preventing overheating of the baby, and avoiding the use of heavy comforters and other soft bedding in cribs.
While these measures work to some extent, they cannot prevent all SIDS deaths. The new study, published in the journal Pediatrics, found that babies who die unexpectedly during sleep are more likely to have low levels of brain chemicals, such as serotonin, in a region called the brain stem. This deficit could prevent them from automatically rousing from sleep when oxygen levels are low.
Babies who have trouble breathing when they’re congested due to a cold, for example, might normally wake up while sleeping to gulp air, but that may not occur in those who have low serotonin in their brain stem.
Kinney and her colleagues examined autopsy data from 71 infants from the San Diego area who died suddenly from 1997 to 2008. They found no difference in serotonin levels between 35 babies who died of suffocation from getting trapped in bedding or a face-down sleeping position and 15 who stopped breathing for unknown reasons. Both groups of babies, however, did have lower serotonin levels on average than a control group of nine infants who died from other causes.
While the new finding needs replication from larger studies, it could eventually pave the way for the development of tests to determine which newborns are most at risk for SIDS. Parents now have no way of knowing. Researchers don’t even know the incidence of these brain stem abnormalities, and treatments to overcome them are also lacking.
Such advances might have saved the life of six-month-old Barrett Tallman, who abruptly stopped breathing during an afternoon nap 20 months ago in a North Carolina day-care center. An investigation revealed that the day-care center had been following the guidelines for safe sleeping.
“My daughter [Barrett’s mother] didn’t think this could happen because they followed all of the recommendations,” said Barrett’s grandmother Lynnette Lowrimore, who lives in Virginia. “Knowing that there was a medical condition in his brain stem that superseded everything they had done provides some comfort, but it also points to the fact that there’s still a ton of work to be done in the research field.”