Last week, a new study about Sudden Infant Death Syndrome (SIDS) went viral after news headlines and social media posts proclaimed that scientists had discovered the root cause of the condition. And a press release describing the research asserted that, thanks to the "breakthrough" finding, SIDS "may soon be a thing of the past."
However, the study in question, published May 6 in the journal eBioMedicine, did not uncover the root cause of SIDS and likely won't contribute to a risk assessment or a way to prevent the syndrome anytime soon, an expert told Live Science.
Rather, the research revealed a potential sign — called a biomarker — that a newborn might have a higher risk of dying of SIDS down the line. The study suggests that there's a link between an infant's risk of SIDS and the activity of an enzyme called butyrylcholinesterase (BChE) in their blood shortly after birth. Infants who die of SIDS had relatively low BCheE activity at birth, as compared with infants who died of other causes or those who survived into childhood, the study found.
"An important aspect of our finding is that it shows that many babies who succumb to SIDS are different from birth," said lead study author Carmel Harrington, a researcher in the SIDS and Sleep Apnoea Research Group at The Children's Hospital at Westmead, in Australia. However, "at this stage, our finding offers nothing new to clinical practice," she told Live Science in an email.
Additionally, previous research suggests that many factors affect infants' risk of SIDS, "so it is unlikely that our finding would apply to all SIDS cases," she added.
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"It is clear that there is no single cause for SIDS," said Dr. Richard D. Goldstein, director of the Robert’s Program on Sudden Unexpected Death in Pediatrics at Boston Children’s Hospital and Harvard Medical School, who was not involved in the research. The new study is an "interesting and solid contribution" to the scientific literature on SIDS, but for now, "the butyrylcholinesterase story is very preliminary and needs a lot more research before we understand its actual significance," Goldstein told Live Science in an email.
What the study actually found
SIDS accounted for nearly 1,250, or 37%, of the sudden unexpected infant deaths (SUID) reported in the U.S. in 2019, according to the Centers for Disease Control and Prevention (CDC).
Broadly, the term SUID describes any sudden and unexpected death of an infant less than 1 year old that has no obvious cause prior to investigation. After investigation, some SUIDs may be attributed to suffocation, physical trauma or some other cause, but if the child's death "cannot be explained even after a full investigation that includes a complete autopsy, examination of the death scene and review of the clinical history," it's classified as SIDS, according to the U.S. Department of Health and Human Services.
Past research largely suggests that infants who die of SIDS have underfunctioning autonomic nervous systems — the division of the nervous system that controls involuntary bodily functions, like respiration, digestion and heart rate, Harrington said. SIDS has been linked to issues with arousal, or the process by which the body transitions from sleep to wakefulness.
SIDS typically occurs during sleep and becomes more likely when caregivers put babies to sleep on their stomachs, as opposed to their backs or sides, according to an editorial published May 19 in the New England Journal of Medicine (NEJM). SIDS rates fell by half in the U.S. during the 1990s, after a federal campaign raised awareness around safe sleeping positions and sleep environments for infants. But since then, the nation's rates of SUID have hovered around the same level — about 90 infants per 100,000 live births — and a large proportion of these deaths are attributed to SIDS.
Subsequent studies have pointed to genetic factors that might raise the risk of SIDS, as well as brain and nervous system differences that may make it difficult for infants to wake up if they stop breathing in their sleep, according to the NEJM report.
"We … decided to test the chemistry of one aspect of the autonomic nervous system, the cholinergic system which, from prior research, is known to play a role in arousal," Harrington said.
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The nerve cells of the cholinergic system use a chemical messenger called acetylcholine (ACh) to communicate, and BCheE serves as one of the key enzymes that helps produce ACh. Because of this, if BCheE activity is low, that means there's less ACh to go around, and this deficiency may undermine the overall function of the cholinergic system, Harrington said.
In their study, the researchers measured BCheE activity in dried blood samples that had been collected from 26 newborns that later died of SIDS. (Dried blood spot tests, or heel prick tests, are conducted shortly after birth to screen babies for diseases like sickle cell and cystic fibrosis, according to the U.K. National Health Service.) The team also analyzed dried blood samples from 30 babies that later died of other unexpected causes, as well as about 550 healthy babies that survived infancy.
On average, the infants who died of SIDS showed lower BCheE activity compared with both the healthy children and those who died of other causes. This suggests that measuring BCheE at birth could help flag infants at risk of SIDS and someday find ways to prevent the syndrome, the authors wrote in their report.
However, "there is a lot of work to do before understanding how specifically it can identify risk," Goldstein told Live Science.
Based on the new study's results, it wouldn't be possible to develop a sure-fire screening test for SIDS based on BCheE alone. Although the SIDS group showed lower BCheE activity than the other groups, overall, at an individual level, their measurements overlapped with those of infants in the healthy group. So in isolation, measuring BCheE wouldn't be a strong indicator of a newborn's future risk of SIDS, The Atlantic reported.
Another limitation of the study is that the team analyzed BCheE activity near the time of birth but not at the time of death, so it's unclear whether the levels remained similarly low at the time the babies died, Harrington said. Plus, the study relied on coroner’s diagnoses rather than autopsy reports to confirm the cause of death, so the true cause of death may have been uncertain in some cases.
In short, there's more work to be done before we fully understand the role of BCheE in SIDS.
Originally published on Live Science.
