Breakthrough in Sudden Infant Death Syndrome

Sudden Infant Death Syndrome
Source: Freepik

Researchers have discovered the first biochemical marker that can help detect those at risk of Sudden Infant Death Syndrome (SIDS).

29 years ago, Dr. Carmel Harrington, an Honorary Research Fellow at Children’s Hospital at Westmead, lost her child to Sudden Infant Death Syndrome (SIDS). She then spent her life searching for the cause of the mysterious syndrome. Now, in a world-first breakthrough, Dr. Harrington and her team have identified a biochemical marker that can potentially save lives. The complete study is available in The Lancet’s journal eBioMedicine.

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 Carmel Harrington, study author

The team of Australian scientists analyzed more than 700 Dried Blood Spots (DBS) taken at birth as part of a newborn screening program. They compared levels of an enzyme called butyrylcholinesterase (BChE) among infants who died from SIDS, infants who died from other causes, and surviving infants of the same gender and date of birth. According to the study, infants who died of SIDS had significantly lower levels of the enzyme. Thus, suggesting the biomarker may play a role in causing the syndrome in infants.

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.

Dr Carmel Harrington, study author

Leading Cause of Infant Mortality in Western Countries

SIDS is also called cot death or crib death. It is the sudden and unexplained death of an apparently healthy child less than a year old. According to the US Centers for Disease Control and Prevention (CDC), the country records more than 3,000 cases of SIDS every year. Although recent public health campaigns have halved the incidence of SIDS, it continues to be the leading cause of infant death in western countries. Moreover, it accounts for almost 50% of all post-neonatal deaths.

Death occurs during sleep, typically between midnight and 9 in the morning. Diagnosis is based on autopsy results, the infant’s medical history, and a complete investigation of the death scene. The exact mechanism behind the syndrome remains unclear. However, doctors believe multiple factors may play a role in causing SIDS. According to the ‘triple risk model’, three simultaneous factors are necessary for death to occur: an underlying biological vulnerability, critical age of development, and an external stressor. Moreover, certain factors such as the infant’s sleeping position, defects in brain regions that control breathing and arousal, and maternal smoking can increase the vulnerability to SIDS.

Despite intensive research over the past decades, identification of any specific vulnerability has remained elusive.

study authors

As a precautionary measure, doctors often advise parents to make the child sleep on their back instead of belly or side. The infant should be placed in a clear space on a firm surface with no fluffy comforters or pillows. Furthermore, co-sleeping is usually discouraged as it can lead to accidental suffocation.

How Do BChE Levels Cause Sudden Infant Death Syndrome?

Along with Acetylcholinesterase, BChE helps hydrolyze the major neurotransmitter Acetylcholine at synapses. The neurotransmitter plays a major role in the autonomic nervous system and controls functions like muscle contractions, heart rate, blood pressure, and breathing. Low BChE levels mean lower neurotransmitter availability at the synapses. Thus, since BChE plays a role in the brain’s arousal pathway, its low levels likely reduce the infant’s ability to cry or arouse in response to environmental threats or difficulty breathing.

According to Dr. Harrington, now that there is evidence of BChE’s involvement, researchers can rely on the biomarker’s levels to assess the risk of SIDS in infants. She believes the study has opened doors for interventions that can prevent future deaths. Furthermore, the team of researchers now plan on investigating ways to address the enzyme deficiency in high-risk babies. And ultimately reduce the risk of SIDS.

Although the findings are promising, experts believe it is far too early to label the biomarker as a cause of SIDS. Further investigations on BChE levels can provide researchers with a more accurate picture of its role in the syndrome. Moreover, the study has quite a few limitations.

Firstly, the team used more than two years old blood samples for their analysis. Therefore, the results do not represent enzyme activity in fresh blood. Secondly, the researchers did not use autopsy findings for a SIDS diagnosis and instead relied on coroners’ diagnoses. Lastly, they included data from children aged 1-2 years while SIDS is defined as sudden death occurring in a child less than a year old.

Nevertheless, this is the first study to identify a biochemical marker that can be measured while the infant is still alive. As researchers continue to investigate this further, experts are advising parents to stick to safe sleeping practices.


Harrington, C. T., Hafid, N. A., & Waters, K. A. (2022). Butyrylcholinesterase is a potential biomarker for sudden infant death syndrome. EBioMedicine, 80, 104041.


Please enter your comment!
Please enter your name here