Infant Sleep Mode Affects Head Control

Babies who sleep on their backs take longer to lift their heads, but benefits overshadow delays, say experts

THURSDAY, Oct. 25, 2001 (HealthDayNews) -- Babies who sleep on their backs seem to take longer learning to lift and control their heads, contends a new study.

But that's OK, child health experts say, because the benefits of back-sleeping -- namely, a significant cut in the risk of sudden, unexplained death -- far outweigh what they consider short-term coordination losses.

Baby deaths from sudden infant death syndrome, or SIDS, also called crib death, have dropped more than 50 percent in the decade since the American Academy of Pediatrics and the federal government launched a nationwide campaign to encourage parents to place babies on their backs at nap time and nighttime, according to Judith Jacobson, executive vice president of the SIDS Alliance.

In 1992, SIDS claimed the lives of more than 5,000 infants, but Jacobson says a new report she received this month from the Centers for Disease Control and Prevention showed 2,151 SIDS cases last year.

"That's a radical, radical shiftÂ…because of the [so-called] back-to-sleep campaign," she says.

Backs still are best for sleeping, despite any developmental bumps along the way, agrees Marian Willinger, a special assistant for SIDS research at the National Institute for Child Health and Human Development.

"The babies eventually will catch up," Willinger says. "We really don't want parents to go nuts about this."

The finding of delayed head control stems from a government-funded study of 205 babies who were delivered prematurely in the mid-1990s at five hospitals around the country -- in Cleveland and Toledo, Ohio, and in Chicago, Los Angeles and Honolulu. The babies were part of a larger group involved in a long-term study of premature infants' physical and mental capabilities, according to Willinger, the government's representative on the study panel.

The researchers checked the babies' abilities to lift their heads and then lower them with control at 56 weeks after conception and again at 90 weeks. For a while after a premature baby is born, medical experts often refer to the baby's age in terms of the number of weeks since the child was conceived rather than the number of weeks since she entered the world. On average, full-term babies are born 40 weeks after conception.

The babies who regularly slept on their backs could not raise their heads to either 45- or 90-degree angles and then lower them with control as well as babies who slept on their stomachs, the study says.

Overall motor skills development, however, did not vary whether the infants slept on their backs, stomachs or sides, the study adds. Details appear in the October issue of the Journal of Developmental and Behavioral Pediatrics.

"The implication is that there's some learning involved," Willinger says. Back-sleeping babies, she explains, simply have not yet had to learn to raise their heads.

"We have always been saying that in order to promote head control and these motor developments that might be a little delayed on the back, you should give the baby 'tummy time,' " she says. "But it must be supervised."

So-called tummy time means placing a baby on his stomach when he is awake and playful. Child development experts say that gives the baby a chance to learn head control.

Babies who sleep on their stomachs rather than their backs, experts say, are more likely to rebreathe pockets of air laden with carbon dioxide -- one of the suspected causes of SIDS.

Although an exact cause of SIDS remains a mystery, scientists now think that certain abnormalities in an infant's brain stem might make the child much more susceptible to sudden death. They suspect the abnormalities could be linked to prenatal exposure to a toxic substance or to a lack of oxygen in the womb, perhaps caused by cigarette smoking during pregnancy.

However, scientists also question whether such abnormalities alone could cause sudden death and speculate that, once the infant is born, things like lack of oxygen, excessive inhaling of carbon dioxide, overheating or even an infection might contribute.

"When sleeping on the stomach, [a baby's] body tends to heat up more easily," Jacobson says. "Heat is trapped in, and babies already have a less developed ability to regulate their own temperature."

"So when placing them on their stomachs with heavy blankets on them, the possibility of overheating is much greater," she says.

"None of these are guarantees," Jacobson adds. "There are babies that continue to die, some of whom have been sleeping on their backs, in smoke-free environments. Their families have done everything right, and they still die. We still can't answer why these babies are dying."

But we do know something that helps, Willinger says.

"It's been shown pretty conclusively, by the experience in a number of countries, including the United States, that when the proportion of infants in a population sleeping on their back [rises], SIDS rates drop," she says. "This is an intervention that works."

Beyond the head-lifting delay, previous research has shown other side effects in infants who sleep on their backs, including a tendency to learn to roll over at a later age and a greater risk of developing a flat head, from spending a disproportionate amount of time on the back.

"But all of the studies that we have supported, looking at long-term outcomes at 18 and 24 months, show that the babies do catch up," Willinger says.

By making sure babies sleep on their backs, she says, "really what you're doing is reducing the risk of death."

What To Do

To read more about babies and sleep -- from the safest positions to how long they should sleep and much more -- go to KidsHealth.

For more on SIDS, check out information from the National Institute of Child Health & Human Development or the SIDS Alliance.

SOURCES: Interviews with Marian Willinger, Ph.D., special assistant for SIDS research, National Institute of Child Health & Human Development, National Institutes of Health, Bethesda, Md.; Judith Jacobson, executive vice president, Sudden Infant Death Syndrome Alliance, Baltimore; October 2001 Journal of Developmental and Behavioral Pediatrics
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