SIDS cause remains a mystery. Scientists think they may have found a promising new clue.

Researchers are one step closer to understanding why some babies are at greater risk of sudden infant death syndrome, or SIDS – the leading cause of death for infants 1 month to 1 year old.

Most of the time, SIDS, sometimes called crib death, happens during sleep. One theory for SIDS is a disruption of a baby’s ability to breathe.

A new study published in the Journal of Neuropathology & Experimental Neurology finds an abnormality in a brain receptor involved in the body’s protective response to gasp for air may play a role. This specific receptor binds to serotonin, a neurotransmitter that’s involved in many processes including regulating mood, sleep, appetite and blood clotting.

The team studied 58 babies whose deaths were classified as SIDS and compared them to a control group of 12 babies whose causes of death were known. The receptor abnormality could be interrupting the normal waking and breathing process, and suggests that a subset of SIDS cases may be related to this, lead author Robin Haynes explained.

“These receptors function to go through what's called autoresuscitation, where the baby senses the low oxygen and they arouse and they gasp, they take that big, deep breath of air, and that helps kick start breathing. It kick-starts the system back up again,” said Haynes, a researcher at the CJ Murphy Laboratory for SIDS Research at Boston Children’s Hospital and Harvard Medical School.

Dr. Panagiotis Kratimenos, a neonatologist at Children's National Hospital, called the finding a "crucial piece of information."

"They're highlighting a part of the brain that can be responsible for this," Kratimenos said. "What they're showing here is how the brain contributes to deaths in those very unfortunate babies by alterations of the signaling that is controlling the breathing and the circulation."

More:What causes SIDS? Study suggests genetics may be at play in sudden infant death syndrome.

What do we know about SIDS?

There are no known biomarkers or tests for SIDS risk, and it’s not yet known what causes it but scientists have been studying potential links.

About 1,389 babies died of SIDS in 2020, the latest year reported by the Centers for Disease Control and Prevention.

Over the past three decades, SIDS rates have declined in the U.S. – dropping from about 130 deaths per 100,000 live births in 1990 to about 38 deaths per 100,000 live births in 2020, according to the CDC. In the 1990s, public health officials began promoting the “Back to Sleep” (now called "Safe to Sleep") initiative to teach parents how to reduce SIDS risk by making sure babies sleep on their backs.

Still, SIDS rates have "plateaued," said Debra Weese-Mayer, Northwestern University professor of pediatric autonomic medicine, highlighting the importance of continued research, education and outreach.

SIDS is part of a larger category called sudden unexpected infant death syndrome, or SUID, which occurs at the highest rates among American Indian and Alaska Native, Black and Native Hawaiian or Pacific Islander babies.

Overall, SUID accounts for about 3,400 unexpected infant deaths a year, CDC data shows.

“We think that SIDS is heterogeneous, meaning there are multiple causes that can contribute,” Haynes said.

She noted while her study suggests serotonin system abnormalities, other studies have suggested genetic predispositions and the involvement of other neurotransmitter receptors.

“They're very likely to be multiple causes or multiple contributing factors … in different SIDS babies. And our challenge moving forward is to figure out how those contributing factors fit together,” she said.

More:Health of Black, Native moms key in fight to improve infant death disparities, experts say

Are there risk factors associated with SIDS?

The National Institutes of Health says some risk factors include sleep position – babies who sleep on their stomachs or sides are at higher risk for SIDS. Babies who are used to sleeping on their backs and are placed in a side or stomach position for sleep, such as during a nap, are at "very high risk" for SIDS, the agency says.

Other risk factors include premature birth, low birth weight, smoking, drug or alcohol use during pregnancy, sleeping on a soft, squishy surface, over-bundling the baby in too many layers of clothing or bedding and bed-sharing.

When it comes to potential biologic causes, Weese-Mayer said the study adds to others suggesting neurotransmitter abnormalities in SIDS.

"Every time there's an investigation into neurotransmitters (and SIDS), we get that much more granular as we need to get," she said.

What can parents do to protect their babies from SIDS?

"There are things parents can do. We always want to advocate for those," said Weese-Mayer, chief of the Center for Autonomic Medicine in Pediatrics at Lurie Children’s Hospital. "While all the science is going on, there's things you could do."

Boston Children’s Hospital recommends the following:

◾ Make sure your baby sleeps on his or her back and on a firm surface.

◾ Keep fluffy blankets or stuffed animals out of the crib.

◾ Don’t overheat the baby or the room.

◾ Refrain from smoking while pregnant and don’t allow smoking near your baby.

◾ Breastfeeding can also lower the risk of SIDS.

Weese-Mayer said other caregivers of a baby should be aware of expert tips too. Parents should make sure "anybody else who comes into contact with this baby is going to respect those recommendations."

More:Does COVID-19 during pregnancy lead to neurodevelopmental problems in babies?

Contributing: Adrianna Rodriguez

Reach Nada Hassanein at nhassanein@usatoday.com or on Twitter @nhassanein.