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The Blog

Is there an enzyme to determine the risk for SIDS?

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Discussing the study done at The Children’s Hospital Westmead in Sydney

Last week, the mainstream media and social media grabbed hold of a study that was done at The Children’s Hospital Westmead in Sydney stating that they found a potential biomarker or enzyme deficit in babies who have died from SIDS.

To back up, I think it’s important we differentiate the difference between SIDS and SUID. Sudden Infant Death Syndrome (SIDS) is a leading cause of infant deaths around the world each year. The most recent statistic we have is that 37% of infant deaths (under one) have been attributed to SIDS. 

SIDS is one part of SUID or Sudden Unexpected Infant Death. SIDS is used to describe a situation where the cause of death was unexplained. Suffocation or entrapment deaths do not fall under the classification of SIDS.

This new study out of Australia was released in a journal called eBioMedicine and has yet to be peer-reviewed. This means that the people who conducted the study are excited about their findings, but fellow experts in the field have yet to confirm it’s validity and use (AKA—is this study even something we should pursue investigating or put into clinical practice?). Please remember that not all research is created equal (the journal it’s released in matters, but more importantly that it has been peer-reviewed). 

The media articles surrounding this have made it seem like we found a solution to stopping SIDS. 

This research study is interesting, but we need way more information.  

The Australia researchers were looking into whether some babies have a defect in the part of the brain that controls arousal from sleep and breathing. The theory was that if the infant stopped breathing during sleep, the defect would keep the child from startling or waking up. 

(I’m about to go into technical aspects of the study, so if you want a summary scroll to the bottom)

The researchers state they were able to confirm this theory by analyzing dried blood samples taken from newborns as part of a Newborn screening program (the heel stick we do for babies in the U.S. and around the world). 

Each SIDS sample was then compared with blood taken from healthy babies. 

They processed samples and calculated these levels for a total of 722 samples. This included 26 sudden deaths (SIDS), 41 non-SIDS, and 655 controls. All deaths occurred over the period from July 2018 to July 2020 and was confirmed SIDS (or not) by a coroner. Their final analysis included 26 SIDS cases compared to 254 Controls and 30 non-SIDS deaths compared to 291 Matched Controls. 

They found the activity of the enzyme butyrylcholinesterase (BChE) was significantly lower in babies who died of SIDS compared to living infants and other non-SIDS infant deaths.

Per their theory, BChE plays a major role in the brain’s arousal pathway, explaining why SIDS typically occurs during sleep. So, they feel per their findings that if we can determine which babies have a deficit in this marker; we can say which babies are more at risk of SIDS. 

Looking at this graph, remember the left side are non-SIDS deaths (the blue being control group AKA kids who did not die and the red being the non-SIDS deaths). For the right side (the blue is the control group and the red are the SIDS-related deaths). 

Looking at the right side, there is a difference in the range of the value of this enzyme, however it is not so large to warrant shock and awe. I do realize there is more of a difference as we compare it to the Non-SIDS side on the left, but there is still overlap between the two groups. 

I would be much more intrigued and wowed if there was not so much of an overlap on the right side (where the blue box was completely in a range above the red box).

But with this overlap, we have to ask ourselves: Was the sample size too small? Are more studies warranted?  (I believe both are needed). 

When I saw the article go viral, regarding SIDS and this study – my first concerns were that people may think: 

  1. “Wow a blood test! That seems easy!”
    • This is not the case yet (or may not be ever) as we need more information. The theory of brain arousal differences is one theory for SIDS, so we need way more information. Is butyrylcholinesterase clinically useful, will it with certainty show that there is a concern for SIDS, AND at what level would the threshold be concerning? 
    • Because there is overlap in the study results, finding a value for BChE that shows us a predictive value for SIDS risk can be difficult. 
  2. “This means that infants have a risk for SIDS and safe-sleep protocols can be relaxed!”
    • PLEASE remember that this is a preliminary study with a small number of participants. Although it could be interesting and intriguing to know more, this doesn’t remove the importance of safe-sleep protocols: Back to sleep, no bumpers, stuffed animals, or blanket in crib until one, no falling asleep with baby on you on the couch, etc.  
    • This study is investigating those cases where a clear reason (AKA suffocation) was not established, so safe-sleep still matters. 
  3. “I can’t wait to ask my doctor for this test!”
    • The article circulated on a Thursday. By Friday, I had two families ask me to do this test. We are not able to do testing for this yet as we need way more information. If further research is done and it does show that screening for this enzyme is valuable (IF!), we would also likely do it with a newborn screen result with all other screening assays. But, we still need way more information.

The circulating article here ended with a very audacious statement saying: “Now that this biomarker has been further confirmed, researchers can turn their attention to a solution. In the next few years, those in the medical community who have studied SIDS will likely work on a screening test to identify babies who are at risk for SIDS and hopefully prevent it altogether.”

The final message on this study regarding SIDS, makes it seem as if this is the answer; when in reality we need way more information.

We know that SIDS/SUID is multifactorial and this COULD be an area of further investigation.

But, it’s one theory among many that the infant safe sleep world is always trying to find answers for. 

As we learn more, please remember not to ask your doctor for this blood test and to continue to follow safe-sleep guidance as you have been.

I will continue to keep you posted via my blog, my Instagram, or my newsletter with up-to-date news in the world of Pediatrics.

P.S. – Sign up for my newsletter here. 

Dr. Mona Admin

Hi there!

I’m a Board Certified Pediatrician, IBCLC, and a mom of two.

I know the ups and downs of becoming a mom and raising kids.

I help moms ditch the worry and second-guessing so you can find more joy in motherhood.


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