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A Chance at Life

Découvrir les sciences de la vie

Death comes without warning: seemingly healthy children fall asleep and don’t wake up. Biochemist Carmel Harrington has found a possible trigger for sudden infant death syndrome (SIDS).

You and your team at Children’s Hospital at Westmead in Sydney have discovered a pivotal biomarker in connection with sudden infant death syndrome.
Carmel Harrington:
This is the enzyme butyrylcholinesterase, in short: BChE. It is an enzyme of the cholinergic system which regulates, among other things, the level of activation of our central nervous system – a process we call arousal. This activation makes sure that we are alert, awake and responsive. In the case of sleep apnea syndrome, where breathing repeatedly stops during sleep, activation ensures that the body awakens. We hypothesize that a deficiency of the enzyme BChE may lead to a reduced arousal response. As a result, the body of the child will simply not respond to a given environmental challenge, whether it be infection, apnea or CO2 rebreathing as a result of prone sleeping.

For decades, scientists have been aware of only potential factors that may promote SIDS, but not its cause. What had been missing?

It is important for me to emphasize that we did not find a cause, but rather a marker of vulnerability. We know that not all infants with low BChE will die. We analyzed enzyme levels in more than 60 infants who had died of SIDS using their dried blood spots taken at birth – at a time when they were still alive. While previous studies had identified biomarkers, those had originated from the blood of babies who had already passed. So our finding raises, for the first time, the real possibility of one day being able to identify infants at risk for SIDS prior to death and to offer appropriate interventions. Someone once told me: “Searching for a biomarker for SIDS is like looking for a needle in a haystack.” Since we were able to establish a connection with the cholinergic system, we are hopeful that one day, we will be able to identify the causes contributing to SIDS.

Our results could one day provide the basis for early identification of potentially vulnerable infants.”
Carmel Harrington

It is possible that you have found the deciding piece of the puzzle. How did it come about?
To start looking at the haystack, you have to make a few assumptions – and mine was that arousal was involved. My doctoral thesis supported this assumption as it showed that infants at risk of SIDS had a marked arousal deficit. As I was a trained biochemist, the next logical step was looking at the enzymes of the cholinergic system, the system that regulates arousal.

In 1991, you lost your son Damien to SIDS. Following this tragedy, you decided to focus your research on this topic. Did your personal history motivate you to persevere until you had reached your goal?

When Damien died, I made a promise that I would leave no stone unturned to try to work out why he died. I often wanted to give up because it was so hard. Many people even thought I was crazy.The final study took much longer than expected due to Covid and as it was completely blinded, I had no idea of what the results were going to be until the very last day when the cases and controls were identified and statistical analysis completed. To be honest, I had come to terms with the idea that the results would in all probability be negative.
So, when on December 21, 2021, I did the final analysis, I was in shock. I could not believe it at first, so I redid and redid the statistics. After that I cried a lot. After all, Damien was the reason for it all. With limited funding available, I had started my fundraising page, Damien’s Legacy, and it is only thanks to the donations I have received through this and the support of the community that we have been able to make this incredible discovery.

This could be the breakthrough for SIDS. What are the next steps? Are there any recommendations or strategies for parents?

Unfortunately, no. A lot more research needs to be done. At this stage, the very best advice I can give is to follow the recommendations and adopt safe infant sleep practices, breastfeed and don’t smoke during pregnancy or expose your infant to environmental smoking. My hope is that one day this finding will enable a capability to screen babies at birth and to offer appropriate interventions so that every baby can go to sleep and just wake up.

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