Sudden infant death syndrome (SIDS) is an unspeakable tragedy in which a healthy baby under the age of one year dies while asleep. Some people call SIDS “crib death” since this is the usual location of the baby at the time of death. Researchers are getting closer to finding the cause for this mysterious syndrome which, to the naked eye, seems unexplainable.

In 2010, for instance, researchers at the National Institute of Child Health and Human Development (NIH), found that levels of serotonin are lower than normal in the tissues of infants that have died of SIDS. Serotonin is a brain chemical that helps to relay messages between cells. The researchers posited that lowered levels of serotonin prevent the brain from responding to breathing challenges, such as lowered levels of oxygen or increased levels of carbon dioxide.

Think about it: you are sleeping face down on your pillow and your nose becomes blocked. Even without waking up, your natural response would be to turn your head so you can get more oxygen. Researchers think that the lowered levels of serotonin in the infant that dies of SIDS means the brain fails to kick in with the self-preservation response that would allow the baby to get more oxygen. Since the baby fails to turn his or her head, the unfortunate result is asphyxiation.

Note that this is only a theory. Still, doctors have LONG known that the rate of SIDS is far lower in babies that are put to sleep on their backs or sides. This was the catalyst for the “Back to Sleep” campaign, begun in 1994 by the Centers for Disease Control and Prevention (CDC), now known as the Safe to Sleep campaign.

A baby that sleeps on its back or side, doesn’t encounter breathing challenges during sleep because there is no partial or full blockage to his or her air passages.

A more recent theory, based on research performed at Boston Children’s Hospital, found abnormalities in the brainstems of infants with SIDS. The portion of the brainstem presenting with abnormalities is known to affect the brain’s ability to control (during sleep) breathing, blood pressure, temperature, heart rate, and arousal from “rebreathing” too much carbon dioxide (from lack of ventilation) or from overheating (overbundling).

Until this point, researchers had theorized that SIDS occurs in healthy babies, presented with breathing challenges during sleep—in other words, babies that were placed in unsafe sleeping environments. The Boston Children’s Hospital researchers decided to question this theory. Were the babies really healthy or were their abnormalities that might have been spotted before the dreadful event?

For purposes of their study, the researchers studied babies that had clearly died of asphyxiation with those that had died of SIDS but had not been placed in unsafe sleep environments at the time of death and were not deemed to have succumbed to asphyxiation. These two groups of infants were also compared to a third group of infants known to have died from a cause other than SIDS. This third group served as a control group.

It was discovered that both groups of babies that died of SIDS had the same brainstem abnormalities. The third group of babies did NOT have these abnormal brainstem findings. As a result, the researchers question the idea that educating parents about unsafe sleeping environments (as a result of putting babies to sleep on their stomachs or near quilts and pillows that might cause suffocation, for instance) sufficiently addresses the issue of SIDS prevention.

The lead author of this study, Hannah Kinney, MD, a neuropathologist at Boston Children’s Hospital stresses that it is still crucial to place infants on their backs and sides during sleep, since there is a real and significant drop in the number of deaths from SIDS in those infants whose parents comply with the Back to Sleep guidelines. “Even the infants dying in unsafe sleep environments had an underlying brainstem abnormality that likely made them vulnerable to sudden death if there was any degree of asphyxia,” Kinney says. “The abnormality prevents the brainstem from responding to the asphyxial challenge and waking.”

Kinney and her team say their findings confirm that an otherwise unexplained death of an infant has to do with vulnerabilities unseen during a regular pediatrician’s examination. Those infants that succumb to SIDS as a result of a compromised sleep situation may have such abnormalities while appearing to be in the pink of health.

“Certainly, there are unsafe sleeping environments that can cause any baby to die, such as entrapment in the crib, but if it’s just sleeping face down, the baby who dies may have an underlying brainstem vulnerability,” says Kinney. “We have to find ways to test for this underlying vulnerability in living babies and then to treat it. Our team is focused now upon developing such a test and treatment.

“Safe sleep practices absolutely remain important, so these infants are not put in a potentially asphyxiating situation that they cannot respond to,” she adds.

SIDS Back-To-Sleep Method

Parents, apparently, are still reluctant to adopt the back to sleep method. Study results presented at a May 3, 2014 meeting of the Pediatric Academic Societies (PAS) showed that only 50% of infants are placed to sleep in the supine position (on their sleeps) in some states, while the overall rate of babies put to sleep on their backs is still only two-thirds.

“Given that supine sleep positioning significantly reduces an infant’s risk for SIDS, it is worrisome that only two-thirds of full-term infants born in the U.S. are being placed back-to-sleep,” said Sunah S. Hwang, MD, MPH, FAAP, lead author of this study, a neonatologist at Boston Children’s Hospital and South Shore Hospital, and an instructor in pediatrics at Harvard Medical School. “More concerning is that adherence to safe sleep positioning is even lower for preterm infants who are at even greater risk for SIDS compared to term infants.”

“Although the precise cause of SIDS is still unknown, we do know that safe sleep practices, such as sleeping on the back, reduces the risk of infant death in the first year of life,” Dr. Hwang said. “The Back to Sleep campaign reduced the rate of SIDS by 50 percent in the 1990s. Since 2001, this rate has remained stagnant.”

Why The Reluctance?

More than 2,000 babies died as a result of SIDS in 2010, the most recent year for which CDC statistics are available. Moreover, SIDS is the leading cause of death in infants between the ages of one month and one year. Why is it then that parents, who constantly crawl the Internet for information and advice on baby care, fail to embrace this basic practice that is such a persuasive element in the prevention of SIDS?

Perhaps it has to do with the quality of a baby’s sleep when the infant is placed on its back? This author once approached the pediatrician to complain her baby didn’t sleep soundly when placed on his back or stomach, to which the pediatrician responded, “That’s the point. You don’t want the baby to sleep so soundly he forgets to BREATHE.”

‘Nuff said.

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