Research reveals new contributing factor to SIDS

Australian researchers have identified a potential cause for sudden infant death syndrome (SIDS), the mysterious diagnosis blamed for the deaths of thousands of babies worldwide every year. But experts caution that the new research, while important, is just one piece of a puzzle.

Each year, more than 1,200 infants under 1 year old die from SIDS in the United States with no immediate or obvious cause of death, according to the Centers for Disease Control and Prevention. Doctors and researchers are unsure which babies are at risk.

On May 6, researchers from the Children’s Hospital Westmead in Sydney published a study in the peer-reviewed journal EBioMedicine that identified a biomarker that could explain how and why SIDS infants die.

In the study, researchers measured levels of the enzyme butyrylcholinesterase (BChE) in blood samples from 67 newborns who died of SIDS and other unknown causes between 2016 and 2020. They then compared these levels with 10 samples from a control group. Researchers found there were significantly lower BChE levels in the children who died of SIDS than in the control group.

The study hypothesizes that the differing levels could be the biological vulnerability behind SIDS.

Biological vulnerabilities are part of the three risk factors, known as the “Triple Risk Model,” normally associated with SIDS. The Triple Risk Model posits that a biologically vulnerable baby at a critical period in development could die from SIDS when exposed to an external stressor, such as a change in the sleeping environment. BChE levels pose a danger because the enzyme is part of the autonomic system that controls functions such as blood pressure and breathing, according to the study.

Dr. Carmel Harrington, who lost her son to SIDS 29 years ago, led the Australian research, the Sydney Children’s Hospitals Network reported.

“My son, Damien, died suddenly and unexpectedly one night. It took me about two years before I could really take a breath again, and at that point, I thought, I actually want to find out why he died,” Harrington said in an interview with the Australian Broadcasting Corp. “Nobody could tell me. They just said it’s a tragedy. But it was a tragedy that didn’t sit well with my scientific brain.”

Despite some media reports, the study does not provide the definitive answer to what causes SIDS. While the research contains good science and adds to the overall understanding of SIDS, it is still preliminary, noted Dr. Richard Goldstein, a SIDS researcher at Boston Children’s Hospital who was not involved in the study. He said further research will be needed to examine a larger population with more recent blood samples.

“It’s a terrible problem, and any contribution is welcome to help to try to understand it better. But there’s a lot more to know before we can call it a breakthrough,” he said. “There’s not just one thing that babies die from in SIDS, and even with the promise of this study, there’s a long way to go.”

Dr. Rachel Moon, chairwoman of the American Academy of Pediatrics Task Force on SIDS, agreed that the results of the study were not definitive due to its small size. She added that while the enzyme levels were statistically different, between individual cases in the Australian study there was an overlap in levels. “It is definitely not confirmed that this is ‘the cause of SIDS,’” she said.

Other lines of research have shown more potential biomarkers for SIDS, Goldstein said. Several studies have identified genetic variants among SIDS deaths that are related to cardiac, respiratory, and neurological functions. Those variants could affect the infant’s arousal pathways—the baby’s ability to respond effectively to changes in the sleep environment.

Because of this, experts advise parents to practice safe sleep habits with babies. According to Mayo Clinic, the risk for SIDS can be increased if a baby sleeps on the stomach, on a soft surface, in a shared bed, or with objects in a crib.