SIDS Rate Drops as More Babies are Placed to Sleep on their Backs or Sides

National efforts to reduce the incidence of Sudden Infant Death Syndrome (SIDS) by placing healthy infants on their backs or sides to sleep appear to have been extremely successful, according to a study funded by the National Institute of Child Health and Human Development (NICHD), reported in the July 22 issue of The Journal of the American Medical Association (JAMA). However, this study and two other NICHD-funded studies in the same issue of JAMA also reported that some segments of the population are more likely than others to place infants to sleep on their stomachs (prone).

In 1992, the American Academy of Pediatrics (AAP) recommended placing healthy infants to sleep on their sides or backs, based on studies showing that infants who were placed to sleep on their stomachs were at greater risk for SIDS. In 1994, the NICHD, in partnership with other agencies of the U.S. Public Health Service, the AAP, the SIDS Alliance, and the Association of SIDS and Infant Mortality Programs, launched the Back to Sleep Campaign, a national campaign that encourages that infants be placed to sleep on their backs.

The first of the three studies, the National Infant Sleep Position (NISP) Study, found that between 1992 and 1996, the prevalence of U.S. infants being placed to sleep on their stomachs has dropped by 66 percent. Although a cause-and-effect relationship cannot be conclusively proven, the rate of SIDS dropped by 38 percent during that period.

The proportion of babies placed prone was higher for older babies. The Boston study found that while only 18 percent of the infants in the study were sleeping prone at 1 month of age, 29 percent were sleeping prone by 3 months of age. The peak incidence of SIDS is between 2 to 4 months of age. In the District of

Columbia study, approximately a third of the mothers who first said they intended to place their infants in a non-prone sleep position, ended up placing their infants prone at 3 months of age.

"These findings indicate the importance of educating all caregivers about continuing the back sleeping position throughout the first year of life," said Marian Willinger, PhD, NICHD Special Assistant for SIDS and lead author of the first study.

Also, all three NICHD-funded studies found that Black infants consistently had a higher prevalence of prone sleeping than did infants in other groups. In 1995 and 1996 the NISP Study found that 43 percent of Black infants in the survey were sleeping on their stomachs, compared with 29 and 24 percent respectively, for the study overall. The second study, conducted in Boston and Toledo, found that 43% of Black infants were sleeping on their stomachs. The third study, conducted in Washington, D.C., found that 44% of Black infants were sleeping on their stomachs.

In the NISP study, 1000 telephone interviews were conducted each spring, from 1992 through 1996, with nighttime caregivers in households having an infant younger than 8 months. During this time, the proportion of babies being placed prone to sleep declined from 70 percent to 24 percent. Simultaneously, the proportion of infants placed to sleep on their backs increased from 13 percent to 35 percent; and the proportion of infants placed to sleep on their sides also increased from 15 percent to 39 percent.

Women were less likely to place infants to sleep on their backs if they had one or more of the following characteristics: race reported as Black, fewer than 16 years of education, had more than 1 child, or lived in southern or mid-Atlantic states.

The study also found that while the back sleep position is very stable, the side position is not. Although babies placed on their sides often roll onto their backs, some roll onto their stomachs; the proportion of those rolling to their stomachs increased with age. This finding supports the recommendation of the American Academy of Pediatrics and the Back to Sleep campaign that the back sleep position is the preferred infant sleep position.

"The success in reducing prone sleeping and SIDS deaths has been accomplished through collaborations between the Federal government, health professionals, concerned families, and industry." Dr. Willinger, said. "Nonetheless, our work is not done. We need a better understanding of why some caregivers still do not place infants to sleep on their backs."

In addition to Dr. Willinger, the study also included researchers from the National Institute on Deafness and Other Communication Disorders, NIH, as well as Harvard Medical School, Boston University, and Children's Hospital, Los Angeles.

The second NICHD-sponsored study, conducted between 1995 and 1996, led by Samuel Lesko, MD, of the School of Public Health at Boston University, found that a significant proportion of infants who were not sleeping on their stomachs at 1 month of age were sleeping on their stomachs by 3 months of age. More than 7,700 women who had given birth at four Boston area hospitals and two Toledo hospitals took part in the study. Switching from nonprone sleeping at 3 months was associated with several maternal characteristics. The likelihood of switching more than doubled for women with less than a high school education, increased by 70% for non-Hispanic Black women, and women with 2 or more previous children, and increased by 50% for Hispanic women of predominantly Puerto Rican descent.

"It seems reasonable that efforts intended to further reduce the prevalence of prone sleeping should be designed to target the population groups who are at particular risk for using this practice," the authors wrote. They recommended that medical practitioners who see infants at well-child visits during the first few weeks of life stress the importance of placing infants to sleep on their backs and keeping them there.

The third study, conducted between 1995 and 1997, led by Ruth Brenner, MD of the Division of Epidemiology, Statistics and Prevention Research at the NICHD, sought to determine which factors predisposed a sample of inner city mothers in Washington, D.C. to place their infants to sleep in the prone position. In this study, 394 mothers were interviewed shortly after delivery and again during a follow-up interview when their infants were between 3-7 months of age.

Forty percent of the 394 mothers indicated at the follow-up interview that they had placed their infant to sleep in the prone position on the night before the interview. Factors associated with placing an infant in the prone position were: Black race, the presence of the infant's grandmother in the home, low income, and intent (as indicated shortly after delivery) to place the infant prone.

Mothers who saw nurses placing their infants to sleep in the prone position in the hospital during the postpartum stay, were also more likely to place their infants prone.

"Ideally, hospitals should adopt and implement policies on infant sleep position that are consistent with current recommendations and should monitor compliance with policies once adopted," the authors wrote.

Approximately a third of the mothers who, shortly after birth, said that they intended to place their infants to sleep on either their backs or sides later indicated that they had placed their infants to sleep in the prone position. The most common reason the mothers cited for placing infants in the prone position was infant comfort.

"Therefore, counseling and reinforcement on the importance of the supine (back) sleep position should continue beyond the initial hospital stay, and, when possible, be directed to both the primary care giver and other extended family members, such as grandmothers," the authors wrote.

The study in the District of Columbia was conducted as part of the National Institutes of Health's Initiative to Reduce Infant Mortality in Minority Populations in the District of Columbia and was co-funded by NICHD and the NIH Office of Research on Minority Health. In addition to Dr. Brenner, the study included researchers from several hospitals, universities, and other institutions in the District of Columbia.

The Back to Sleep campaign distributes free brochures, posters, public service announcements, and videos urging that infants be placed to sleep on their backs. Along with the message that placing infants to sleep on their backs can save lives, the Back to Sleep campaign emphasizes other steps that parents can take to help reduce the risk of SIDS. These include: placing babies to sleep on a firm surface free of fluffy bedding and soft toys or pillows; making sure expectant mothers receive early and regular prenatal care; providing a smoke-free environment before and after the baby is born; avoiding smoking, drinking alcohol, or using drugs (unless prescribed by a doctor) during pregnancy; ensuring that babies don't get too warm when sleeping; contacting a baby's doctor or clinic right away when a baby seems sick; ensuring that babies receive their immunizations on schedule; and, when possible, breastfeeding.

The campaign's website is available through the NICHD home page and free campaign materials are available through its toll free hotline, 1-800-505-CRIB.

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