Study identifies potential biomarker for SIDS: Researchers say they have found the reason why infants die from Sudden infant death syndrome


Sudden infant death syndrome (SIDS) – sometimes known as “cot death” – is the sudden, unexpected and unexplained death of an apparently healthy baby. In the UK, around 200 babies die suddenly and unexpectedly every year. This statistic may sound alarming, but SIDS is rare and the risk of your baby dying from it is low.



Dr Iceman

SIDS is devastating and I would be elated if a cause was discovered. This type of research is firmly in my professional wheelhouse. I was thrilled when I saw proclamations that the cause of SIDS had been discovered, and that parents don’t have to worry about risk anymore!

I understand that the lead author of the study lost her own child to SIDS, which is devastating. It makes sense and it is admirable that she would be so devoted to researching the cause.

While this study has found something that warrants further investigation, the hype on this finding is unwarranted and gives false hope at best. At worst, it will lead parents to think that they can safely abandon safe infant sleeping practices.

The authors are claiming that the enzyme Butyrylcholinesterase (abbreviated BChE) is a potential biomarker for SIDS. Okay, that seems reasonable. They analyzed dried blood samples from newborns for the amount of BChE.

hey had 2 main groups of infants. Those that had died from SIDS, and those that had died from non-SIDS causes. For each 1 of the infant deaths, they matched them by age and sex with ~10 infants that are still alive.

They compared the BChE levels of the infants that had died from SIDS to their matched (living) controls. They similarly compared the BChE levels of the infants that had died from non-SIDS causes to a different group of matched (living) controls.

The infants that had died from SIDS had lower BChE levels than their controls, while the infants that had died from non-SIDS causes did not differ from controls. That is the finding of the study. So that means they found the cause of SIDS, right? Sadly, NO. Far from it.

BChE is a type of cholinesterase, which are enzymes that break down the neurotransmitter acetylcholine (abbreviated ACh). The most famous cholinesterase is called acetylcholinesterase (AChE). AChE and BChE are similar enzymes.

The ACh system is a diffuse neuromodulatory system. It has lots of actions and widespread targets throughout the body. It’s most famous for making skeletal muscles contract and for being the communicator for the “rest and digest” arm of the autonomic nervous system.

The ACh system is also implicated in arousal from sleep. So it can make someone wake up, or have muscle spasms, but could also make them relax, depending on what cells in the body it’s acting on? Oh, it can also stop your heart. You can see how this gets complicated.

The only other two studies of cholinesterases in SIDS showed: 1) no difference in AChE between SIDS and control. 2) HIGHER AChE in SIDS compared to control. That’s the opposite of the current study.

Cholinesterases like BChE and AChE break down ACh, which would decrease ACh amount. So if BChE is decreased, ACh activity should increase (it’s more nuanced than this, but oh well).

So if BChE is low in SIDS, ACh activity would be increased, and we know that high ACh activity causes SIDS, right? We do not. Autonomic dysregulation is suspected, but we don’t know exactly in which direction and which arm is to blame (“fight & flight” or “rest & digest”).

Plenty of other suspected causes of SIDS. The prevailing model, the “triple-risk hypothesis” is the best idea we have at this point. It involves an infant with an underlying vulnerability, at a certain age, with an environmental stressor. All 3 things converge in SIDS.

Could the low BChE be the underlying vulnerability? Maybe. I don’t think it is, but I’d be thrilled to be wrong! Only future studies will tell. Back to the paper…

There were only 26 SIDS deaths and 30 non-SIDS deaths represented. That is a small number. Certainly too small to make sweeping claims.

They omitted 6 patients’ results from the non-SIDS death group because their BChE values “fell below the standard curve”. Remember, the claim is that values are lower in SIDS deaths. There were no omissions from other groups.

That is a small difference. While their tests showed it was significant, looking at the data puts things in perspective. Is THAT the cause of SIDS? I don’t think it is, unfortunately. The variability in the groups is huge. Guess I have to start a new thread now.

New (continued) thread: The SIDS BChE study contains mostly speculation. It’s okay to speculate a bit in scientific articles, but this paper is primarily speculation.

There are a lot of claims that are not supported by data, and references to solid studies that are only loosely relevant, but connected in kind of a hand-wavey fashion.

I don’t want to get into the details on this thread, but I will quote one passage: “…it has been suggested that BChE may be involved in maintaining ACh levels in the arousal systems of the central nervous system”

This passage is followed by a citation to a fairly old paper that doesn’t even mention ACh, let alone BChE. Not sure what got screwed up with the references there, but that is a main thing that the paper hinges on.

I forgot to mention that the SIDS death group is (by definition) no older than 12 mos. They included kids up to 24 mos in the non-SIDS death group, which they do fairly list as a limitation.

SIDS is a diagnosis of exclusion, with unknown cause (by definition). The underlying causes of SIDS are likely varied, and while there may be commonalities in many cases, there are surely a variety of etiologies.

My beef isn’t really with the paper. It’s with the irresponsible press coverage. I don’t really want to tweet the quotes, but I’ll do a couple just so I can help other people understand that they are not accurate.

“On Saturday, researchers… released a study that confirmed not only how these infants die, but why”


Blood marker identified for babies at risk of SIDS hailed as ‘breakthrough’

By Nancy Lapid

May 14, 20221:36 AM GMT+8Last Updated 3 hours ago

NEW YORK, May 13 (Reuters) – A team of Australian researchers have identified a biochemical marker in the blood that could help identify newborn babies at risk for sudden infant death syndrome (SIDS), a breakthrough they said creates an avenue to future tragedy-preventing interventions.

In their study, babies who died of SIDS had lower levels of an enzyme called butyrylcholinesterase (BChE) shortly after birth, the researchers said. BChE plays a major role in the brain’s arousal pathway, and low levels would reduce a sleeping infant’s ability to wake up or respond to its environment.

The findings are game changing and not only offer hope for the future, but answers for the past, study leader Dr. Carmel Harrington of The Children’s Hospital at Westmead in Australia said in a statement.

“An apparently healthy baby going to sleep and not waking up is every parent’s nightmare and until now there was absolutely no way of knowing which infant would succumb,” Harrington said. “But that’s not the case anymore. We have found the first marker to indicate vulnerability prior to death.”

Using dried blood spots taken at birth as part of a newborn screening program, Harrington’s team compared BChE levels in 26 babies who later died of SIDS, 41 infants who died of other causes, and 655 surviving infants.

The fact that levels of the enzyme were significantly lower in the infants who subsequently died of SIDS suggests the SIDS babies were inherently vulnerable to dysfunction of the autonomic nervous system, which controls unconscious and involuntary functions in the body, the researchers said.

The Sydney Children’s Hospital Network in Australia called the discovery “a world-first breakthrough.”



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