New research offers clues as to why some babies die of SIDS

Scientists in Australia have found that some babies at risk of SIDS have low levels of the enzyme butyrylcholinesterase (BChE) in their blood. Their study, published May 6 in the journal eBioMedicine, could pave the way for newborn screening and interventions if the results are confirmed by further research.

“It’s the first time we’ve ever had a potential SIDS biomarker,” said Dr. Carmel Harrington, who led the study at the Children’s Hospital of Westmead, in Sydney, Australia.

Researchers have been trying to get rid of the biological underpinnings of the enigmatic syndrome for decades. And while public health campaigns have dramatically reduced the incidence of SIDS, it remains a leading cause of sudden and unexpected death in infants under 1 year of age in Western countries. In the United States, about 3,400 babies die suddenly and unexpectedly each year, according to the Centers for Disease Control and Prevention. This includes babies who die suddenly from a known cause, such as suffocation, as well as babies who die without an obvious cause, such as SIDS. Nearly half of sudden and unexpected infant death (SUID) cases in the US are due to SIDS.

One of the reasons SIDS remains so tragic and mysterious is because it’s likely not caused by a single biological mechanism, but by a combination of factors that come together in a perfect storm, said Dr. Thomas Keens, a pediatric pulmonologist at Children’s Hospital Los Engelen. Previous studies have pointed to low activity or damage in areas of babies’ brains that control, for example, heart rate, breathing and arousal from sleep, as well as environmental stressors such as soft bedding or secondhand smoke.

“The thinking among researchers is that some babies die of SIDS because they don’t wake up in response to a dangerous situation when they sleep,” said Dr. keens.

To test whether there was anything inherently different in SIDS babies, Dr. Harrington and her colleagues dried blood samples from the newborn heel prick test from 655 healthy babies, 26 babies who died of SIDS and 41 babies who died of other causes. They found that about nine out of 10 babies who died of SIDS had significantly lower BChE levels than the babies in the other two groups.

“I was just stunned,” said Dr. Harrington, who has been seeking clues and crowdfunding for her research for nearly 30 years since she lost one of her own children to SIDS. “Parents of SIDS babies carry a huge amount of guilt because their child essentially died on their watch. But what we found with this study is that these babies are different from birth, the difference is hidden and nobody knew about it before. So it is not the fault of the parents.”

The new findings support researchers’ hypothesis that babies dying from SIDS have problems with arousal, said Dr. Richard Goldstein, a pediatric palliative care specialist at Boston Children’s Hospital. BChE plays a role in the availability of important neurotransmitters in the arousal pathway of the brain. Low levels of the enzyme may indicate that the brain is unable to send out signals that tell a baby to wake up and turn her head or gasp. “But we need a lot more research before we can understand its true meaning,” said Dr. Goldstein.

While the study identifies an important chemical marker in a small group of infants, it’s too early to say whether widespread testing for BChE will be helpful.

First, scientists and doctors don’t know what a “normal” level of the enzyme looks like. And because the Australian researchers didn’t have access to fresh blood samples for BChE, they didn’t measure absolute levels of the enzyme. There was also overlap between the babies. Some of the babies who died of SIDS had BChE levels in the same range as the babies who didn’t die.

“If you’re going to test every baby born, you want the results to be abnormal only for very high-risk babies,” said Dr. keens. Even if further studies were to help refine the test for BChE to accurately distinguish between babies who could die from SIDS and those who could lead healthy lives, doctors and parents would still be faced with a dilemma: what to do next. to do? Currently, there is no intervention or treatment for low BChE levels.

Much of the advice for preventing SIDS remains the same, said Dr. keens. Be sure to follow safe sleep recommendations, such as laying your baby on her back — both during the nap and at night. Remove loose sheets, blankets, pillows, pads and soft toys from your baby’s sleeping area. And consider keeping your baby in the same room as you overnight for at least six months, or, ideally, until your baby turns one year old.

The American Academy of Pediatrics also recommends avoiding exposure to smoke, alcohol, and illegal drugs during pregnancy; breastfeeding; routinely immunize; and using a pacifier to reduce the risk of SIDS.

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