SIDS rate has declined, but 2,300 U.S. babies still die annually


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August 5, 2013

I still put my 2-year-old to sleep on his back even though each morning he’s snuggled on his tummy, head shoved into a corner of his crib. The “back to sleep” message has become ingrained in my new-parent psyche, as the campaign to reduce Sudden Infant Death Syndrome was designed to do when it began 20 years ago after studies showed that placing babies to sleep on their stomachs tripled their SIDS risk.

SIDS, in which an infant dies during sleep from an undetermined cause, can be a huge source of anxiety for new parents — and rightly so. Even after Back to Sleep efforts helped cut the SIDS rate by more than half from 1994 to today, it is still the leading cause of death among U.S. infants aged 1 month to 1 year, with 2,300 cases annually.

The latest research into SIDS is giving parents clearer guidelines for protecting babies during sleep. For example, a recent analysis of more than 1,400 SIDS cases found that having a baby sleep in the parents’ bed increases the risk of SIDS by a factor of five for infants younger than 3 months old. Bed sharing presents a risk because, as Children’s National Medical Center pediatrician Linda Fu explains to new parents, the airflow around the baby may not be good enough, “and that is all it takes.”

In the past decade, researchers identified how low oxygen levels, combined with an underlying brain defect, can cause SIDS. Scientists believe a triple-risk model explains many SIDS cases: A baby has a defect in an area of the brain that controls breathing and arousal; the baby is at an age when those brain areas are still immature; and the baby is exposed to an external stress that compromises his breathing or oxygen levels, or that causes overheating.

“To have a SIDS death, you have to have at least one of those [factors], and you have a higher risk if you have two or three of those happening at the same time,” says Fern Hauck, a professor of family medicine at the University of Virginia School of Medicine in Charlottesville.

A problem of oxygen flow

Sleeping face down on a soft surface or with soft bedding that can press up against the face can decrease a baby’s oxygen flow too much. When this happens, a normal baby will auto-resuscitate by gasping, crying, turning his head or moving. “It’s thought that SIDS infants have a defective arousal mechanism, which means they stay in that position and gradually suffocate,” Hauck says. Overheating is thought to lead to SIDS in a similar way, by suppressing an infant’s arousal response.

The Back to Sleep public-health campaigns — now named Safe to Sleep — solved much of the problem, as parents were told that sleeping on the back was best for babies. The SIDS rate fell dramatically, from almost three in 2,000 live births in the late 1980s, to one in 2,000 live births now.

Many parents have stopped using soft bedding and bumper pads in cribs (the sale of bumper is even banned in Maryland) and switched to wearable blankets to lower the risk of suffocation.

Yet since 2001, “the SIDS rates are not falling as one might hope,” says Bob Carpenter, the medical statistician at the London School of Hygiene and Tropical Medicine who led the bed-sharing study. He calculates that if all preventable risk factors — including mothers’ smoking while pregnant, babies’ sleeping on their stomach and bed sharing — were eliminated, the rate of SIDS would drop more significantly, to close to 1 in 10,000 live births.

The connection between brain defects and SIDS was raised definitively in 2010, when researchers at Children’s Hospital Boston discovered that SIDS babies were deficient in the brain-signaling chemical serotonin in the brain stem. In fact, according to some research, 50 to 75 percent of infants who die of SIDS have a serotonin defect. In a study published this year, Kevin Cummings, a physiologist at the University of Missouri in Columbia, showed that he could improve auto-resuscitation in newborn rats that had genetically lowered serotonin levels by giving them caffeine. Because caffeine is an effective treatment to stimulate breathing in premature infants, Cummings says it may hold promise as a SIDS prophylactic in high-risk infants.

Other researchers have found that about 10 to 15 percent of SIDS deaths can be traced to babies with a genetic predisposition for long QT syndrome, a heart rhythm disorder that can go undetected and lead to cardiac arrest, says Marta Cohen, a pediatric pathologist at Sheffield Children’s Hospital in England. Also, SIDS researchers say smoking tobacco while pregnant may cause a rewiring of the unborn baby’s brain in areas important for breathing and arousal, making maternal smoking one of the largest risk factors for SIDS.

It’s conceivable that newborns might one day be screened for low serotonin levels in the brain stem or for genes that are involved in faulty arousal, Cohen says, but that day is far off.

So what should parents of newborns do?

According to Hauck, who helped write the American Academy of Pediatrics guidelines about SIDS, parents should:

●Avoid smoking, alcohol and illegal drugs during pregnancy and after birth.

●Place the baby on his back every time he is put to sleep.

●Use a firm sleep surface, with no soft objects or loose bedding in the crib.“Putting a baby into an empty crib looks awful, like you are torturing them,” Hauck acknowledges. “But the truth is, the babies don’t really care.” All that comfy stuff is really for the parents, she says.

●Share bedrooms but not beds. Many SIDS researchers believe an uptick in bed sharing may explain the plateauing of SIDS rates in developed countries. They report that 50 to 70 percent of new SIDS cases in the past few years have occurred in a bed-sharing scenario.

“We’re now in the position we were 20 years ago with sleeping prone,” Carpenter says. “If we could get rid of bed sharing, the whole picture could change with SIDS. That’s our hope.”

●Practice breast-feeding. No one is sure why this helps, but breast-fed babies have a lower risk.

●Consider using a pacifier for naps and bedtime (after the first month, if the baby is breast-feeding).

●Avoid overheating the baby and the baby’s room.

●Follow the routine immunization schedule.

●Finally, avoid products marketed as reducing the risk of SIDS. (None have been proved to do so.)

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