Landmark study finds first biomarker to detect babies at risk of SIDS

Sudden infant death syndrome (SIDS) is one of leading causes of infant death and until now researchers have not been able to identify any specific physiological factor that may make a baby more vulnerable. A team of researchers in Australia have now identified a blood biomarker linked to brain arousal that could potentially be used to identify infants most at risk of SIDS.

Over the last few years infant deaths from SIDS have been greatly reduced as researchers have identified more and more environmental factors that play a role in this horrifyingly unpredictable event. But despite these advances SIDS still accounts for around 50 percent of all infant deaths in Western countries.

SIDS is thought to be a multi-factorial event, meaning it takes several factors to occur simultaneously for an infant to be struck. The current hypothesis to explain SIDS is known as the “triple risk model.”

This model suggests three factors must coalesce at the same time for SIDS to occur: a physiologically vulnerable infant, a critical period of development, and an external stressor. Researchers have identified several external stressors that contribute to SIDS risk – from sleeping face down to exposure to tobacco smoke.

“An infant will die of SIDS only if he/she possesses all three factors; the infant's vulnerability lies latent unless subjected to an exogenous stressor during the critical period,” the researchers write in the new study. “Despite intensive research over the past decades, identification of any specific vulnerability has remained elusive.”

The new study focused on a particular enzyme called butyrlycholinesterase (BChE). This enzyme plays a role in the brain’s arousal system and the researchers hypothesized a deficiency in BChE may make an infant more vulnerable to the other factors that contribute to SIDS.

“Babies have a very powerful mechanism to let us know when they are not happy,” said Carmel Harrington, lead researcher on the project. “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.”

The researchers looked a BChE levels in dried blood spot samples taken from 722 babies at birth. Out of the cohort of babies, 67 died suddenly and unexpectedly between the ages of one week and two years. Of the deaths, 26 had been classified as SIDS-related and 41 were non-SIDS.

Compared to the infants dying of other causes, and a control group of healthy infants, the SIDS cases showed significantly low levels of BChE at birth. According to Harrington this indicates low levels of the brain arousal enzyme may make an infant more vulnerable to SIDS.

“What this research shows is that some babies don’t have this same robust arousal response,” said Harrington. “This has long been thought to be the case, but up to now we didn’t know what was causing the lack of arousal. Now that we know that BChE is involved we can begin to change the outcome for these babies and make SIDS a thing of the past.”

Moving forward, the researchers urge for more work to validate their findings. As this is the first measurable blood biomarker that could be used to indicate SIDS risk the goal would be to incorporate BChE testing into standard newborn screening protocols. This could allow parents and doctors to identify infants at high risk of SIDS and incorporate greater protections against known external triggers.

Harrington also hopes to begin working on ways to address this particular enzyme deficiency so those babies found with low levels of BChE could be further protected.

“This discovery has opened up the possibility for intervention and finally gives answers to parents who have lost their children so tragically,” concluded Harrington.

The new study was published in the journal eBioMedicine.

Source: The Sydney Children’s Hospital Network