Smoke Found to Heighten Risk of Infant Death
Exposure to tobacco smoke is a much bigger risk factor for sudden infant death syndrome than was previously suspected, and keeping newborns away from tobacco smoke could reduce the death rate from SIDS by nearly two-thirds, British researchers reported today.
In the largest study of its kind, encompassing more than 350,000 births over a two-year period, the team also found that allowing an infant to sleep on its side doubles the risk of death compared to sleeping on its back, a previously unsuspected finding.
As many as a third of parents in England have adopted side-sleeping for infants because of the high risk of SIDS previously linked to sleeping face down, according to the study. Having babies sleep on their sides reduces the risk of SIDS, but not as much as sleeping on their backs, the researchers said.
Reporting in the British Medical Journal, the team said that in addition to being kept away from tobacco smoke completely, if infants were placed on their backs to sleep and wrapped only in light blankets, the SIDS death rate in England could be reduced to less than a quarter of what it is today.
The reduction would be even higher in the United States because so many infants are still allowed to sleep on their stomachs, said Dr. Peter Fleming of the University of Bristol, who headed the study. Even so, preliminary efforts to control infant sleep positions have cut the U.S. incidence of SIDS to about 0.91 deaths per 1,000 live births, down from 1.3 in 1991.
The next concern that needs to be addressed is smoking, said neurobiologist Marian Willinger, special assistant for SIDS at the National Institute of Child Health and Human Development.
“The data are really coming together that we need to go after cigarette smoking more heavily,” she said. The health risks of tobacco are becoming “a major concern,” she added, because of the rise in smoking among young women of child-bearing age.
For every hour spent each day in a room where people smoke, the risk increases 100%, Fleming said. If an infant spends four hours per day in such a room, he or she is four times as likely to die of SIDS as a child not exposed to tobacco smoke.
“Of all the epidemiological studies [about SIDS] that I have seen, this is the most thorough,” said neurologist James McKenna of Pomona College. “It shows that exposure to tobacco smoke is phenomenally important.”
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The new data are particularly important, Willinger said, because this is the first large study conducted in a population where the majority of infants no longer sleep on their stomachs. As the result of an intensive Back to Sleep campaign conducted in England, the number of SIDS deaths there has dropped by two-thirds over the last five years.
Eliminating the deaths linked to prone sleeping makes it much easier to measure the importance of other factors, she said.
The United States is in the midst of a similar campaign that has resulted in a 30% reduction in SIDS deaths over the last two years--from about 6,000 deaths per year to about 4,200. The goal is at least a 50% reduction.
Current estimates are that about 29% of infants in the United States are still permitted to sleep on their stomachs and 32% on their sides, Willinger said. Infants below the age of 6 months are generally not able to roll over on their own; when placed on their backs, they stay there.
Other risk factors for SIDS include a lack of prenatal care, low birth weight and drug and alcohol abuse by the parents, but these risks are considered lower than those for sleep position and tobacco exposure. Last year, researchers identified an abnormality in brain chemistry that also appears to make some infants more susceptible to SIDS risks.
As sleep position is being brought under control, researchers and advocates are turning to other risk factors that are now becoming relatively more important, and tobacco is first on the list. The new study “is a clarion call to parents to stop smoking around their babies and to not let anyone else do so either,” said Phipps Y. Cohe, director of national public affairs for the SIDS Alliance.
Fleming and his colleagues monitored every birth over a two-year period in three National Health Service districts in England encompassing 17 million people. Among the 350,000 births, there were 198 “cot deaths,” as the British call them.
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Nurses visited the families of each one of the infants that died, as well as 800 carefully matched control families with healthy infants, and asked a long set of questions that illuminated risk factors.
The nurses found that placing the babies on their sides to sleep doubled the risk of SIDS compared to sleeping on their backs, most likely because the infants roll onto their stomachs, Fleming said. If parents stopped placing infants on their sides, he said, the death rate would go down 20%.
An equally large risk was associated with wrapping the children heavily, having loose bedclothes that can entangle the infants or using heavy comforters, which allow the children to overheat. Parents should place infants in a “feet-to-foot” position, with their feet against the bottom of the bed, so they cannot slip under the covers, he said.
That measure and stopping use of heavy wrappings would reduce the death rate another 17%, he said.
But it was the risk associated with tobacco that was “really astonishing,” Fleming said. “The risk of dying increases directly in proportion to the number of cigarettes smoked in the household and the number of hours per day that the infant spends in a room where someone has smoked.”
The study also investigated bed-sharing--sleeping with a parent--which some studies had suggested was statistically linked to SIDS. The team found that there was no increased risk associated with bed-sharing if the mother does not smoke. If the mother smokes, an infant who sleeps with her is four times as likely to die of SIDS--perhaps from toxins in her breath or emanating from her clothing.
If all parents had their children sleep on their backs, kept them away from tobacco smoke and controlled bedding, Fleming said, “our calculations suggest that we could reduce cot deaths by 75%.” That would be a 90% reduction from the rate five years ago before the Back to Sleep campaign began, he said.
Transferred to the United States, his results suggest that the number of deaths could be reduced to only 600 per year.
“But we must keep in mind that some children are still dying of SIDS in a smoke-free environment,” said the SIDS Alliance’s Cohe. “While we want to get the word out about tobacco, we must continue seeking additional risk factors and underlying causes.”
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Fighting SIDS
Sudden infant death syndrome kills an estimated 4,500 babies in the United States each year, down about 30% over the last two years as a result of the Back to Sleep campaign. Nearly 90% of the deaths occur in the first six months of life, most of them in cold-weather months. Boys are at a slightly higher risk than girls, and twins and triplets are at a slightly higher risk than individual babies.
Things parents should know and do to minimize the risk of SIDS:
During pregnancy
* Get early prenatal care.
* Don’t smoke (either parent), drink or use illicit drugs.
After the baby is born
* Place the baby on his or her back to sleep unless your physician specifically recommends otherwise.
* Use firm bedding materials; do not use a water bed.
* Do not wrap the baby too tightly, which risks overheating. Do not keep the nursery too warm. If you use comforters or heavy blankets, place the baby’s feet to the bed’s footboard so he or she cannot slip completely beneath the covers.
* Don’t allow anyone to smoke around the baby or allow the baby to spend time in rooms where people smoke.
* If either parent smokes, do not take the baby to bed with you.
* Breast-feed if possible.
More information
* National Institute of Child Health and Human Development’s Back to Sleep hotline: (800) 505-CRIB
* SIDS Alliance hotline: (800) 221-7437
Source: Dr. Peter Fleming, University of Bristol
