Scientists claim to have found a biomarker of Sudden Infant Death Syndrome (SIDS), a “world-first breakthrough” that has the potential to someday reduce the number of babies dying unexpectedly.

Researchers from the Children's Hospital at Westmead in Australia found that levels of an enzyme called butyrylcholinesterase (BChE) were significantly lower in babies who later died of SIDS. 

Since BChE is known to play a role in the brain’s arousal pathway, the researchers argue a deficiency of the enzyme likely reduces an infant’s ability to wake or respond to the external environment, raising the risk of SIDS.

The research was recently published in The Lancet’s journal eBioMedicine. It was led by Dr Carmel Harrington, Honorary Research Fellow at Children's Hospital at Westmead, who lost her own child to SIDS 29 years ago and has since dedicated her career to uncovering the cause of this tragic syndrome. 

“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. But that’s not the case anymore,” Dr Harrington said in a statement.

“Babies have a very powerful mechanism to let us know when they are not happy. Usually, if a baby is confronted with a life-threatening situation, such as difficulty breathing during sleep because they are on their tummies, they will arouse and cry out. What this research shows is that some babies don’t have this same robust arousal response,” she explained.

SIDS, sometimes known as "cot death," is the sudden and unexpected death of a seemingly healthy baby less than one-year-old. The CDC estimates there are around 3,400 cases of SIDS and other unexpected infant deaths in the US every year. Thankfully, rates of the syndrome have been declining since the 1990s, although there are still major racial and ethnic differences, particularly among Native Americans, Alaska Natives, and Black people.

To reach their findings, the team looked at BChE levels in 722 Dried Blood Spots (DBS) taken at birth as part of the Newborn Screening Program. Levels of BChE were measured in both SIDS-related deaths and infants dying from other causes, then compared to 10 surviving infants with the same date of birth and gender.

Armed with this knowledge, the team says babies could potentially be screened for BChE to give parents and doctors an understanding of whether they are at a higher risk of SIDS. The researchers also hope to follow up the research by looking at ways to address the enzyme deficiency and actively reduce the risk of SIDS in high-risk babies.

“This discovery has opened up the possibility for intervention and finally gives answers to parents who have lost their children so tragically. These families can now live with the knowledge that this was not their fault,” Dr Harrington commented. 

While the findings are promising, some groups have called for some caution when reading bold headlines about the research.

"The findings of this study are interesting and more work needs to be done," the Lullaby Trust, a British charity aiming to prevent unexpected deaths in infancy, said in a statement sent to IFLScience.

"While research is underway, we urge all parents and carers with infants to continue following the evidence-based safer sleep advice to reduce the risk of SIDS occurring. This includes: always sleeping baby on their back in a clear sleep space on a flat, firm and waterproof mattress with no bulky bedding, pillows or cot bumpers," they added. 

"Claims that a cause of SIDS has been found could give false hope to families whose baby has died suddenly and unexpectedly and may downplay the continued importance of the safer sleep advice."

Updated 13/05/2022: This article has been updated to include a statement from the Lullaby Trust.

Correction: An earlier version of this article incorrectly claimed a cause for SIDS may have been found. It has been corrected to reflect that a biomarker that may increase the likelihood of the syndrome was instead identified.