Infants accustomed to sleeping on their backs who are then placed to sleep on their stomachs or sides are at an increased risk for SIDS-greater than the increased SIDS risk of infants always placed on their stomachs or sides. The study, conducted by Kaiser Permanente in Northern and Southern California and supported by the National Institute of Child Health and Human Development (NICHD) and the National Institute on Deafness and Other Communications Disorders (NIDCD), appears in the current issue of the American Journal of Epidemiology.
The study also shows that infants sleeping on their sides are at an increased risk of SIDS. The researchers think that a large part of the risk may be due to the instability of the side sleeping position and the tendency for infants sleeping in this position to turn onto their stomachs.
The study, which was conducted in 11 counties in Northern and Southern California, is the first to examine the relationship between infant sleeping position and SIDS in a racially diverse U.S. population. The incidence of SIDS has declined over 50 percent since 1992, when the American Academy of Pediatrics recommended that infants be placed on their backs to sleep. Before the current study, evidence of the link between stomach sleeping and SIDS risk was based largely on overseas studies, where populations and cultural practices are different from those in the United States.
"These findings reinforce the importance of placing infants on their backs at all times," said Duane Alexander, M.D., Director of the NICHD. "This is the first study of infant sleeping position in relation to SIDS risk to be conducted completely after our 'Back to Sleep' campaign was launched in 1994. It provides us with important information that will inform the campaign's future messages."
The research team included De-Kun Li, M.D., Ph.D., senior investigator with Kaiser Permanente's Division of Research in Oakland, CA. He and his colleagues completed in-person interviews with 197 women whose infants had died of SIDS and with 312 mothers of living infants. Each SIDS infant was compared to a living infant of the same race and age, and born in the same county. Both sets of women answered questions about infants' sleeping positions, including:
- the position in which the infant had last been put down to sleep
- the position in which the infant was found
- changes in sleeping position since birth, during the two weeks before death, and on the death date
The researchers also collected information about bedding materials, type of mattress, room- or bed-sharing, room temperature, exposure to passive smoking, and infant sickness.
The researchers found that infants last placed on their sides for sleep were twice more likely to die of SIDS than infants last placed on their backs. In addition, the risk of SIDS was significantly increased if infants turned from their sides to their stomachs during sleep. While the reason isn't clear, the researchers think that the instability of the side position makes it more likely for babies who are placed to sleep in this position to roll over onto their stomachs.
A pattern also emerged when the researchers looked specifically at the position in which an infant was last placed to sleep, compared to their usual sleeping position. If an infant who was usually placed to sleep in the low-risk position-- on the back--was then placed to sleep in a high-risk position (the stomach or side), his or her SIDS risk was seven to eight times greater than that of an infant who was always placed to sleep on his or her back.
"The message here is 'every night and nap time count'," said study co-author Dr. Marian Willinger of NICHD. "Parents and caregivers should place their babies on their backs every time they go to sleep. Consistency is the key."
One of the strengths of this study is that the researchers interviewed a racially- and culturally diverse group of mothers-White, African American, Hispanic, and Asian/Pacific Islander, although the small sample size limited the researchers' ability to examine risk within each racial group. This study provides results from the first study of infant sleeping position in relation to SIDS risk to be collected entirely after the NICHD's "Back to Sleep" campaign was launched to inform the public about the importance of sleep position in preventing SIDS.
The NICHD and the NIDCD are part of the National Institutes of Health (NIH), the biomedical research arm of the federal government. NIH is part of the U.S. Department of Health and Human Services. The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. NICHD publications, as well as information about the Institute, are available from the NICHD Web site, http://www.nichd.nih.gov, or from the NICHD Information Resource Center, 1-800-370-2943; e-mail NICHDInformationResourceCenter@mail.nih.gov. The NIDCD supports and conducts research and research training on the normal and disordered processes of hearing, balance, smell, taste, voice, speech and language and provides health information, based upon scientific discovery, to the public. For more information about NIDCD programs: www.nidcd.nih.gov.