Scientists identify biomarkers behind sudden infant death

Australian researchers have identified what may be the first explanation of why some healthy infants die in their sleep, a condition known as Sudden Infant Death Syndrome (SIDS), which is one of the leading causes of fatality in children younger than the age of 12 months and an occurrence linked with devastating psychological impact on parents.

At play could be an enzyme called butyrylcholinesterase (BChE), which is responsible for waking – or arousing -- the brain from sleep in case there is a threat to life, like obstructed breathing. The study found that blood taken from infants who died from SIDS showed significantly less amount of BChE than those that survived.

“Babies have a very powerful mechanism to let us know when they are not happy,” lead researcher Carmel Harrington said, according to a statement last week by the Sydney Children’s Hospital, where the team is based.

“Usually, if a baby is confronted with a life-threatening situation, such as difficulty breathing during sleep because they’re on their tummies, they will arouse and cry out,” Harrington was cited as saying. “What this research shows is that some babies don’t have this same robust arousal response.

For their study, which was published in the latest edition of the journal eBioMedicine (a part of the The Lancet’s publications), dried blood spot samples taken 2-3 days after birth from 722 babies were analysed. It found that the enzyme was “lower in babies who subsequently died of SIDS compared to surviving controls and other non-SIDS deaths”.

SIDS fatalities occur when a seemingly healthy baby dies unexpectedly in sleep. Their exact share in deaths in India was not immediately available – estimates from decades ago pegged this at a prevalence rate of 3.9 per 1,000 births. But in estimates from other countries, SIDS can account for as much as 50% of the deaths in healthy children under the age of 1 year.

The nature of the deaths leaves a particularly profound psychological impact on parents.

Researcher Harrington cites the death of her son Damien close to 30 years ago as her motivation to study SIDS. “Twenty-eight years ago, I was a lawyer, who used to be a research biochemist and a mother of 3 gorgeous children, when one night my beautiful healthy baby son, Damien, died suddenly and without warning. I was told it was tragic and I was told to go home and enjoy my living babies and have more. I tried,” Harrington wrote in a fundraiser appeal for the research in 2018.

Three years after her son’s death, the child of a friend of hers too died, an event that particularly precipitated her decision to undertake the study. “…the sad fact remains that in Australia nearly 3 babies die suddenly and unexpectedly every single week.”

According to the Sydney Children’s Hospital statement, the researchers will now begin looking at introducing the BChE biomarker into newborn screening and develop specific interventions to address the enzyme deficiency. “It is expected this will take around five years to complete,” it said.

“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,” Harrington said.