Research helps uncover the causes of SIDS

By Amy Norton HealthDay Reporter

THURSDAY, May 25, 2023 (HealthDay News) — Researchers have found another clue as to why some infants suddenly die while sleeping, and it’s linked to a faulty chemical receptor in the brainstem.

Experts said the findings provide another piece of the puzzle for understanding the root causes of sudden infant death syndrome (SIDS).

By examining autopsied brain tissue, the researchers found that a particular chemical receptor was altered in the brain stems of babies who died of SIDS, compared to infants who died of other causes.

The receptor, called serotonin 2A/C, is thought to play a key role in helping a sleeping infant wake up and seek air in response to oxygen deprivation.

“This 2A receptor is very important in arousing them as a defense mechanism,” said Robin Haynesa Boston Children’s Hospital researcher who led the study.

She pointed out that the underlying biology of SIDS is complex and no one is saying an abnormal serotonin receptor is the sole culprit. It’s thought, Haynes said, that there are multiple mechanisms at work, and they can vary from infant to infant.

But for at least some infants who succumb to SIDS, dysfunction of that particular brain receptor may be a reason, she noted.

“This study gives us one more insight into the intrinsic vulnerability to SIDS,” Haynes said.

Many people may know that SIDS is related to sleeping position and environment, including the fact that sleeping on the stomach can increase the risk for the infant.

In 1992, the American Academy of Pediatrics began advising parents to put their baby to sleep on their back, not their stomach. The federal government, meanwhile, launched a “Get Sleepy” campaign to raise awareness, and by 1998 the national rate of SIDS had dropped by 45%.

However, this decline has stopped. In total, about 3,400 infants die suddenly each year in the United States, of which about 1,400 die from SIDS, according to the United States Centers for Disease Control and Prevention. Many of the other deaths are caused by accidental suffocation or strangulation while sleeping.

So, over the years, experts have advised additional measures for safe sleeping, such as putting babies to sleep only in a bassinet or bassinet with a flat, firm mattress, and keeping the area free of soft bedding, toys, and crib pads. Parents should also put their baby to sleep in their room, but not in their bed.

But SIDS involves more than environmental factors, Haynes said.

There must be underlying biological reasons why some infants are vulnerable—characteristics that make them unable to respond normally when an environmental stressor, such as stomach sleeping, impairs their breathing.

Haynes and his colleagues studied tissue taken from the San Diego medical examiner’s office that was linked to the deaths of 70 infants. SIDS was the cause in 58 cases, while 12 infants died of other causes.

The researchers found that the serotonin receptor was altered in the brainstems of infants who died of SIDS.

Gail Bagwell is a clinical nurse specialist in neonatology at Nationwide Children’s Hospital in Columbus, Ohio. She said there is a critical period in infant development when SIDS occurs – usually between 2 and 4 months, but up to 6 months.

It is thought that biological vulnerability and environmental stressors, such as bed sharing, coming together during this time can lead to SIDS.

As for the underlying biology, Bagwell agreed there would likely be no single culprit. She noted that a recent study, for example, found that blood samples from infants who died of SIDS had reduced activity of an enzyme called butyrylcholinesterase, compared to infants who died of other causes.

This enzyme plays a key role in the production of a chemical along the brain’s “wake-up” pathway.

Yet another recent study, involving siblings of infants who died of SIDS, suggested that genetics put some babies at increased risk: These siblings’ risk of SIDS was four times higher than average.

How all of these different findings might fit together, Bagwell said, is unknown at this time.

Haynes made a similar point. “We are gradually putting the pieces of the puzzle together,” she said.

But while only some infants may have underlying vulnerabilities to SIDS, it’s essential that all parents and caregivers follow safe sleep practices, the two experts said.

For one thing, these steps also protect infants from accidental suffocation and strangulation. On the other hand, there is no way to identify infants particularly vulnerable to SIDS.

This may change in the future. Haynes said one of the ultimate goals is to find out if there’s a “biomarker” — something that can be easily measured in blood, for example — that shows whether a newborn is at increased risk for SIDS.

The American Academy of Pediatrics has advice on sleep safe for infants.

SOURCES: Robin Haynes, PhD, senior fellow, pathology, Boston Children’s Hospital, Harvard Medical School, Boston; Gail Bagwell, DNP, APRN, CNS, Division of Neonatology, Children’s National Hospital, Columbus, Ohio; Journal of Neuropathology and Experimental Neurology, May 25, 2023, online

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