Clues emerge about possible factors in Sudden Infant Death Syndrome

Sudden Infant Death Syndrome, the unexpected and unexplained death of a baby less than a year old, is by definition a mystery. But researchers are getting closer to understanding some of the risk factors and mechanisms that contribute to SIDS.

The prevailing theory points to three possible factors: first, the infant is at a critical stage of development during its first year of life. Second, the baby is exposed to a stressor, such as sleeping on his stomach, which can reduce the amount of oxygen in his blood while increasing the level of carbon dioxide. And third, the infant has an underlying abnormality that makes surviving this traumatic event more difficult.

A study published Thursday in the Journal of Neuropathology & Experimental Neurology points to such an anomaly.

Researchers from Boston Children’s Hospital and Rady Children’s Hospital in San Diego have found that a particular brain receptor is likely involved in helping babies breathe. was modified in some infants who died of SIDS. The receptor in question is part of the serotonergic system, which plays an important role in regulating involuntary bodily functions such as heart rate, breathing, and blood pressure.

SIDS usually occurs while an infant is sleeping, and although rare, it is the leading cause of death in babies between the ages of one month and one year in the United States. The Centers for Disease Control and Prevention attributed nearly 1,400 infant deaths to SIDS in 2020.

To better understand the disease, the researchers behind the new study examined brain tissue from 58 infants who died of SIDS between 2004 and 2011, then compared those samples to brain tissue from 12 infants who died from other causes, such as than pneumonia or heart disease. . The results showed that babies who died of SIDS were more likely to have an altered version of the brain’s serotonin-related receptor than control cases.

Robin Haynes, lead author of the study and a researcher at Boston Children’s Hospital, said babies normally have a protective response that causes them to gasp when they don’t get enough oxygen while they sleep.

“They wake up and they go through what’s called self-resuscitation, where it gets the breathing going again,” she said.

With SIDS, however, this response may not trigger, perhaps because of the altered brain receptor. If an infant is unable to restore breathing and heart rate, it can impede blood flow and oxygen delivery.

A series of theories about SIDS

The Boston-based research group behind the new study has studied the relationship between SIDS and serotonin for about three decades and has published several papers based on various analyzes of the same brain tissue samples.

These samples are among the only ones available to SIDS researchers. But that small sample size makes it difficult to draw strong conclusions about potential causes or risk factors, according to Dr. José Javier Otero, director of neuropathology at The Ohio State University College of Medicine.

“It’s almost, from a scientific point of view, brave to even try to try to draw a conclusion,” Otero said.

Yet researchers have long suspected that serotonin plays a role in SIDS given its association with breathing.

“It makes perfect sense that serotonin is a key player,” said Dr. Debra Weese-Mayer, chief of the pediatric independent medicine division at Lurie Children’s Hospital in Chicago. “The question is: is he the only player?

It’s likely that genetics also affect an infant’s vulnerability to SIDS, though scientists aren’t sure in what capacity, Weese-Mayer said.

Another factor may be infections that infants acquire early in life, according to Dr. Michelle Caraballo, pediatric pulmonologist at Children’s Health in North Texas and assistant professor at UT Southwestern.

“SIDS rates are highest in the winter. That’s also when we see the highest rates of viral infections in babies,” she said.

How Parents Can Reduce Their Baby’s Risk

No tests exist to reveal if a baby has an underlying predisposition to SIDS – and as no cause has been confirmed, there is no treatment to reduce an infant’s risk. But Haynes said the researchers haven’t given up on that perspective.

“Once you’ve identified an infant with a particular abnormality, the goal is to one day have preventative therapy, but what that looks like we can’t tell yet,” she said.

However, there are still ways to protect against SIDS.

The CDC recommends that parents place sleeping babies on their backs at all times. A baby’s sleeping area should be firm, flat, and free of lint and bedding such as blankets, pillows, and protective pads. Parents should not cover their baby’s head while sleeping, and babies should ideally sleep in the same room as their parents until they are at least 6 months old.

The American Academy of Pediatrics also suggests giving babies a pacifier at nap time and at bedtime once they are comfortable breastfeeding.

Breastfeeding has been shown to reduce the risk of SIDS, while drinking alcohol or smoking during pregnancy may increase the risk.

“We want people to follow safe sleep guidelines as much as possible,” Caraballo said. “What’s really scary is that it’s possible to do everything right and the baby still dies. At the end of the day, we don’t know the exact cause of death in the majority of cases.”