Genetic Understanding of SIDS
Groundbreaking research at Rush unlocking genetic links with SIDS
Until relatively recently, not much was known about what sudden infant death syndrome is, though much was known about what it is not. Sudden infant death syndrome, or SIDS, claims approximately 2,500 young lives in the United States every year. Recent research is pointing to a possible genetic basis for this devastating disorder.
"We began to consider that there was a genetic basis for SIDS, because so many parents had done everything right, the baby was always on her or his back, the parents never smoked — they had followed all the rules," says Debra E. Weese-Mayer, MD, professor of pediatrics and director of pediatric respiratory medicine at Rush University Medical Center. "We listened carefully to these families and realized that they had done everything they were supposed to do, but still their babies died of SIDS."
One of the first things that Weese-Mayer and her colleagues explored was a genetic marker that was associated with serotonin reuptake. "Those babies with this marker had the potential to process serotonin more efficiently, which may initially sound like a good thing. However, this efficient reuptake made the neurotransmitter less available for autonomic functions."
Serotonin is a chemical messenger, or neurotransmitter, that is involved in a broad range of physiological systems and is also involved in autonomic nervous system regulation. The autonomic nervous system regulates those body functions that are often considered automatic or involuntary, like blood pressure control, the pumping of the heart, breathing and temperature regulation.
"We found a significant association between having this marker for overly efficient serotonin uptake and death from SIDS," says Weese-Mayer. She and her colleagues have also found a link with SIDS and a gene (PHOX2B) involved in the development of neurons that produce serotonin and in determination of cell fate in the autonomic nervous system.
"For babies who have died from SIDS, we want to be certain they do not have a potentially related disease that also affects the autonomic nervous system," says Weese-Mayer. "This can be determined by testing for the PHOX2B gene mutation that is characteristic of congenital central hypoventilation syndrome (CCHS). Both SIDS and CCHS are diseases that fit into the rubric of autonomic nervous system dysregulation. For CCHS we know the genetic basis and can now do prenatal screening for families with an affected infant"
Weese-Mayer and her colleagues are also looking at links between SIDS and genes related to nicotine metabolizing. "We know that the mother smoking and exposure to secondhand smoke put the baby at risk, so we're interested in seeing what the genetic basis for this risk may be," says Weese-Mayer.
"Back to Sleep" to Reduce Risk
"Though our research is giving us a better understanding of possible genetic mechanisms for SIDS, we recognize that these mechanisms may act independently or in combination with environmental cofactors," says Weese-Mayer. "The Back to Sleep recommendations have been effective but we need to keep them visible to parents, caretakers, and health care professionals. If anything, I would like to see these recommendations become even more visible and available to anyone in contact with a pregnant woman or young infant."
While parents continue to comply with known modifiable risk factors for SIDS, we will continue to aggressively research candidate genes that might heighten an infant's vulnerability from SIDS. With nearly 2300 infants dying from SIDS each year in the U.S. alone, we are thoroughly committed to our research into the genetic basis for SIDS.
For more about SIDS and the Back to Sleep recommendations, read the Reducing the Risk of SIDS section of "SIDS Research Brings New Understanding."
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