Researchers from the SIDS and Sleep Apnoea Research Group in the Children’s Hospital at Westmead in Australia reportedly found a potential risk factor for sudden infant death syndrome (SIDS), the specific cause of which has eluded scientists for decades.
Media reports of the study hailed the findings as a “breakthrough discovery” in SIDS, which refers to the unexplained death of an infant less than one year old. A viral tweet claimed that researchers had found the cause of the syndrome. Carmel Harrington, PhD, a sleep researcher and lead author of the study, even proclaimed that SIDS may soon be “a thing of the past.”
The study, published in The Lancet’s eBioMedcine, compared blood samples from more 700 newborns, including 26 who died of SIDS and 30 who died of different causes in their first couple years of life.1
The researchers found that the babies who died of SIDS had a lower level of the enzyme butyrylcholinesterase (BChE). A deficiency of BChE could present “inherent vulnerability” to SIDS in some infants, they said.
However, some noted that while the findings offered a first step, they came with several limitations and the authors didn’t establish BChE levels as an exact cause for the syndrome.
“This paper produces suggestive evidence that there may be some correlation between this enzyme and SIDS. I don’t think we can say that it pinpoints the reason that infants die from SIDS in any way,” said Mary Beth Howard, MD, MS, MSc, pediatric emergency medicine physician at the Johns Hopkins Children’s Center and assistant professor of pediatrics, who is not affiliated with the study.
Though the study result provided some valuable insight on BchE, Howard said that putting too much stock in this enzyme could create a “false sense of security” among parents, and that following safe sleep practices remains crucial to preventing SIDS.
Reducing the Risk of SIDS with Safe Sleeping Practices
The best way to minimize the risk of SIDS is to set them up to sleep in a safe environment, according to the National Institute of Child Health and Human Development (NICHD) Safe to Sleep initiative. Lay the baby on their back when they are too young to turn themselves over. Use a firm, flat mattress and keep it clear of clutter, like pillows, blankets, and toys.
Stomach sleeping and the presence of clutter can increase the odds of airway obstruction, overheating, and carbon dioxide build-up when a baby re-breathing their own exhaled breath.2
The NICHD also says that parents can reduce the risk of SIDS by receiving regular prenatal care, avoiding smoking and using drugs during pregnancy and immediately after, breastfeeding, and taking the child for routine check-ups.
What We Know About SIDS
Sudden unexpected infant deaths have been on the decline since the 1990s, when public health campaigns emphasized the importance of safe sleeping practices. Still, there were about 1,250 deaths from SIDS in 2019, according to CDC data.
The “triple-risk hypothesis” proposes that infants may die of SIDS only if they meet three conditions—they are within six months old, have an underlying vulnerability, and experience an environmental stressor.
When babies are in the first several months of life, they undergo many drastic changes in sleeping patterns and functions like variations in breathing and body temperature. Some infants are especially vulnerable to SIDS due to defects in certain parts of their brain and genetic mutations that affect breathing, the heart, and other organs.
When faced with an environmental stressor—like second-hand smoke, stomach sleeping position, and overheating—an already vulnerable baby may not be able to survive.
There’s currently no way to test for a child’s risk of developing SIDS. Because SIDS is such a complex and multi-faceted diagnosis, it can be difficult to pinpoint the culprit.
“There’s no numeric or no way to calculate what is what an infant’s specific risk for SIDS is,” Howard said. “There are other factors, such as the environment and maternal factors, that we know put an infant at risk for SIDS. How all of those interplay and the weight that certain risk factors have in relation to others is less well known.”
What Did the Study Actually Find?
Researchers suspected dysfunction in the cholinergic system—a major part of the nervous system that deals with brain functions like sleep, waking, and attention—may contribute to SIDS. BChE, in conjunction with other enzymes, works to regulate the cholinergic system.
To test whether there is a link between BChE and SIDS outcomes, the researchers analyzed dried blood samples from some newborns who died. They matched each infant who died with about 10 living infants of similar age and sex and compared the amount of enzyme in each group.
Those that died from SIDS had lower BChE levels than the living children, while those who died of non-SIDS causes had about the same amount of the enzyme as the control group.
Low levels of this enzyme could indicate that the cholinergic system is not functioning at full capacity. Though not all babies with low levels of BChE will succumb to SIDS, the researchers wrote that a deficit of the enzyme in babies who died from SIDS “represents a measurable, specific vulnerability prior to their death.”
The findings open up new potential for research, Howard said. But this particular study isn’t large or precise enough to draw any conclusions—the study only included 26 SIDS deaths and 30 non-SIDS deaths.
The authors reported measuring the enzyme in 1.7 to 23.3 units per milligram for healthy newborns, compared to 2.9 to 10.8 for those who died of SIDS. While the average BChE levels differed between the groups, there was a fair bit of overlap. Without a specific threshold for the enzyme level linked to SIDS-related death, Howard said it would be difficult to develop a blood test to screen for the syndrome.
Where Scientists Go From Here
Researchers are continuing to investigate how brain abnormalities, certain genetic mutations, and other factors could contribute to SIDS risk.
Harrington said her team will continue to investigate the role of the cholinergic system. All the funding for the research was provided by a crowdfunding campaign in honor of Harrington’s late son, who died of SIDS before his second birthday.
“I know that in three to five years’ time, this will be a thing of the past. But to get us there, we need a lot of funding,” Harrington told Heather du Plessis-Allan in a podcast.
Howard is less hopeful that scientists will find a definite cause for SIDS so quickly. It will take much more extensive studies and a deeper understanding of the connection between BChE and SIDS outcomes. For instance, she said, there may be observable differences other than BChE between babies who died from SIDS and those who didn’t.
“I know that there is a lot of active ongoing research trying to find one thing that we can use to ascribe an infant’s risk for dying of SIDS. I’m optimistic that that may happen, but I don’t think that this study is the answer,” Howard said. “Maybe in our lifetime, we will see that, but I’m not sure. It’ll be challenging.”
