Genetics may make some babies vulnerable to SIDS or 'cot death,' study says

The genetic mutations linked to SIDS are found in fewer than 5 out of 100,000 people. Photo / 123rf

Sally Clark lost both her infant sons shortly after their births. In 1996, 11-week-old Christopher fell unconscious after being put to bed and never woke up. Two years later, 8-week-old Harry was found dead slumped forward in his bouncy chair.

Doctors initially concluded the first boy had died of sudden infant death syndrome (SIDS) — in which a seemingly healthy baby dies without warning and without an obvious cause. But after Clark's second child died, prosecutors in the United Kingdom charged her with murder and put her on trial. According to scholars analyzing the widely publicized case, Clark was wrongly convicted based on a statistic. An expert witness for the prosecution claimed the chance of two cases of SIDS, in an affluent family like hers, was astronomically high — 1 in 73 million.

Her defenders said the numbers assumed that SIDS strikes at random, even though we had no idea back then whether that was true, according to The Washington Post.

An important study published Wednesday in the Lancet shows a link between SIDS and a rare genetic mutation that would make some families more vulnerable than others — providing a possible explanation for situations like Clark's.

The research involved 278 infants who died of SIDS, also called "crib death" or "cot death," and 729 healthy controls. Four of those who died of SIDS had a variant of a gene called SCN4A associated with an impairment of breathing muscles, while no babies in the control group had it. Authors Michael Hanna from the United Kingdom's Medical Research Council's Center for Neuromuscular Diseases and Michael Ackerman from the Mayo Clinic in the United States wrote that these mutations are typically found in fewer than 5 out of 100,000 people.

The paper stressed that genetics is just one of the factors that could contribute to SIDS and explained the "triple risk hypothesis": A vulnerable infant, during a critical period in development, is exposed to an external stress.

The researchers suggest that the genetic mutation could leave some babies with weaker respiratory muscles, so they would be unable to correct their breathing as quickly or as well while they are sleeping in reaction to things like tobacco smoke or a stressful sleep position.

"Our study is the first to link a genetic cause of weaker breathing muscles with sudden infant death syndrome and suggests that genes controlling breathing muscle function could be important in this condition. However, more research will be needed to confirm and fully understand this link," Hanna said in a statement.

Hanna and Ackerman noted that the study has several limitations, including the fact that all the participants were white and of European ancestry, so it's unclear whether other racial and ethnic groups would be affected in the same way.

In the United States, infants in minority groups, including American Indians and African Americans, tend to have a higher risk of SIDS than their white counterparts. In total in 2015, the most recent year for which figures are available from the Centers for Disease Control and Prevention, 1,600 babies had died of SIDS.

Since 1994, the National Institute of Child Health and Human Development has been advocating a "Back to Sleep" approach to educate parents about how putting babies to sleep on their backs can reduce the risk of SIDS. The American Academy of Pediatrics's sleep guidelines urge parents to sleep in the same room but not in the same bed as infants.

As for Clark, her conviction was overturned on appeal after she had served three years of a life sentence. She died in 2007 at her home. No cause of death was given. A statement issued by her family expressed sadness and anger at her situation, stating that "she never fully recovered from the effects of this appalling miscarriage of justice."

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