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CD Summary Article: Sleeping Position and Sudden Infant Death Syndrome
Best practices to reduce the risk of SIDS
Sleeping Position and Sudden Infant Death Syndrome
Narrative taken from July 7, 1998 CD Summary Issue, Vol.47 No.14
SUDDEN INFANT Death Syndrome (SIDS) is the sudden death of a child under one year of age that remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history. 1
It is the second leading cause of infant deaths in Oregon and the third leading cause of infant deaths in the United States. 2,3
From biblical times until the 20th century, virtually all sudden infant death was attributed to suffocation by a mother sleeping in the same bed. As it became common for infants to sleep alone, it became clear that this explanation was incomplete. 4
Simply rolling over onto the hapless infant and smothering him was considered a common cause of death in the 19th century - often attributed to inebriated slum dwellers - or others who were obviously different from the pontificator. By the 1970s, "overlaying" was generally considered to be impossible and was rarely reported. 5
There has been a series of hypothesized causes of SIDS, each of which has subsequently been disproved. These included hypersensitivity to cow's milk, viremia, myocardial conduction defects, and spontaneous, idiopathic central apnea. One cause of sudden infant death that often cannot be distinguished from SIDS is infanticide, which may constitute as much as one to five percent of SIDS deaths. 6
Factors that were associated with increased incidence of SIDS included low birthweight, preterm birth, low maternal age, high parity, maternal smoking and drug use and poverty. 7
Sleeping in a prone position (ventral side down) emerged as a possible cause of SIDS in the 1970s. 8
Historically most pediatricians had assumed that putting an infant to sleep on its back would increase the incidence of aspiration and pneumonia, but early work led to the conclusion that putting infants to sleep prone decreased SIDS. 9,10
The evidence in support of this theory was the dramatic reduction in SIDS mortality in many countries after parents were advised to abandon the prone position and instead put their infants to sleep on their back or side. 11-14
Experimental work has subsequently shown that when babies sleep in the prone position with their noses embedded in soft surfaces, they rebreathe their own exhaled air, which contains high levels of carbon dioxide. It is likely that susceptible infants have blunted arousal systems and therefore do not react appropriately to elevated levels of carbon dioxide by lifting and turning their faces to the side. 15,16
Infants of mothers who smoke in pregnancy have deficient hypoxic awakening responses. 17
Thus, maternal cigarette smoking during fetal life may subtly damage critical control centers in the brain stem, leaving the infant at unsuspected risk for failure to detect high levels of inhaled carbon dioxide. 11
In 1992, the American Academy of Pediatrics (AAP) released a statement recommending that healthy infants be placed for sleep on their side or back, rather than being placed prone (on their stomach). The recommendation was based on numerous reports from other countries that showed that the prone sleeping position is associated with a higher incidence of SIDS. 18
In 1994, AAP and others collaborated to initiate a national Back to Sleep campaign to encourage parents and caregivers to place healthy infants on their backs when putting them down to sleep. They added a recommendation that soft surfaces that might trap exhaled air should not be in an infant's sleeping environment. 19
Since 1992, NIH has surveyed sleep position, showing that prone sleeping in the United States has decreased from 70% to 24%. 20
At the same time, the SIDS death rate has fallen 38% in the United States and 40% in Oregon. 21
Several studies have concluded that the decrease in prone sleeping is the reason for the decrease in SIDS. 19,22,23
More recent reports indicate that the risk of SIDS is slightly greater for infants placed on their sides compared with those placed on their backs. 24,25
There is some evidence that the reason for this difference is that infants placed on their sides have a higher likelihood of spontaneously turning to a prone position. However, both nonprone positions (side or back) are associated with a much lower risk of SIDS than the prone position. In 1992, there was concern that sleeping supine might be associated with an increase in adverse events. Careful monitoring by English researchers has found no such increase. 26
A study of child care centers in 1996 found that many child care providers place infants to sleep in the prone position. Two states have found that more than one-third of SIDS deaths occur in organized child care settings. 27
As nonprone sleeping has become more common, the dominant modifiable risk factor for SIDS has become exposure of the infant to tobacco. Maternal smoking is associated with a three-fold increase in risk of SIDS; 28
risk is also increased if the father smoked. 29
In Oregon, 17.6 percent of mothers smoked during their pregnancy in 1996, a reduction since 1990. 30
Individual physicians/practitioners who wish to provide brochures to their patients may obtain bulk copies of SIDS - BACK TO SLEEP literature by calling 503-731-4021. These are available in both English and Spanish. Health practitioners can also obtain display posters, stickers and take-home reminder cards. Individual parents or the general public can obtain materials by calling Oregon SafeNet at 1-800- SAFENET (1-800-723-3638) or in the Portland area, 306-5858. Glossy door hangers are also available as a night time reminder to parents when putting their baby to bed.
Best practices to reduce the risk of SIDS:
- Place your baby on its back to sleep
- Don't smoke if you are pregnant*
- Provide a smoke-free environment for your baby
- Avoid overheating your baby
- Whenever possible, breastfeed your baby
- Make sure both mother and baby have regular health check-ups
*(or even if you're not)Learn more about safe sleep for babies
- Willinger M, James LS, Catz C. Defining the Sudden Infant Death Syndrome (SIDS): Deliberations of an expert panel convened by the National Institute of Child Health and Human Development. Pediatr Pathol. 1991;11:677-684.
- Center for Health Statistics, Oregon Health Services. Oregon Vital Statistics Annual Report, 1995, Vol 2, March 1998.
- Guyer B, Martin JA, MacDorman MF, Anderson RN, et al. Annual summary of vital statistics -1996. Pediatrics 1997;100:905-918.
- Thach BT. Sudden infant death syndrome: old causes rediscovered? N Engl J Med 1986;315:126- 128.
- Bass M, Kravath RE, Glass L. Death-scene investigation in sudden infant death. N Engl J Med 1986;315:100-105.
- McClain PW, Sacks JJ, Froehlke RG, Ewigman BG. Estimates of fatal child abuse and neglect, United States, 1979 through 1988. Pediatrics 1993;91:338-343.
- Kraus JF, Bulterys M. The epidemiology of sudden infant death syndrome. In: Kiely M, ed. Reproductive and Perinatal Epidemiology, CDC Press, Boca Raton, 1991
- Beal SM, Blundell H. Sudden infant death syndrome related to position in the cot. Med J Aust 1978;2:217-218.
- Beal S. Sleeping position and SIDS. Lancet 1988;ii:512.
- Lee NNY, Chan YF, Davies DP, Lau E, Yip DCP. Sudden infant death syndrome in Hong Kong: confirmation of low incidence. BMJ 1989;298:721.
- Valdes-Dapena M. A half century of progress: the evolution of SIDS research. In: Rognum TO, ed. Sudden Infant Death Syndrome: New Trends in the Nineties, Scandinavian University Press, 1995.
- Beal SM, Finch CF. An overview of retrospective case-control studies investigating the relationship between prone sleeping position and SIDS. J Pediatr Child Health 1991;27:334-339.
- deJonge GA, Engelberts AC, Koomen-Liefting AJM, Kostense PJ. Cot death and prone sleeping position in the Netherlands. BMJ 1989;298:722- 724.
- Wigfield RE, Fleming PJ, Berry PJ, Rudd PT, Golding J. Can the fall in Avon_s sudden infant death rate be explained by changes in sleeping position? BMJ 1992;304:282-283
- Kemp JS, Thach BT. Sudden death in infants sleeping on polystyrene-filled cushions. N Engl J Med 1991;324:1858-1864.
- Kemp JS, Thach BT. A sleep position-dependent mechanism for infant death on sheepskins. Am J Dis Child 1993;147:642-646.
- Lewis KW, Bosque EM. Deficient hypoxia awakening response in infants of smoking mothers: possible relationship to sudden infant death syndrome. J Pediatr 1995;127:691-699.
- American Academy of Pediatrics Task Force on Infant Positioning and SIDS. Pediatrics 1992;89:1120-1129.
- Willinger M, Hoffman HJ, Hartford RB. Infant sleep position and risk for sudden infant death syndrome; report of meeting held January 13 and 14, 1994, National Institutes of Health, Bethesda, MD. Pediatrics 1994;93:814-819.
- AAP Task Force on Infant Positioning and SIDS. Positioning and sudden infant death syndrome (SIDS): Update. Pediatrics. 1996;98:1216-1218.
- 1996 data on SIDS from Oregon Health Services, Center for Health Statistics, personal contact.
- Dwyer T, Ponsonby AL, Blizzard L, et al. The contribution of changes in the prevalence of prone sleeping position to the decline in sudden infant death syndrome in Tasmania. JAMA 1995; 273(10):783-789.
- Spiers PS, Guntheroth WG. Recommendations to avoid the prone sleeping position and recent statistics for sudden infant death syndrome in the United States. Arch Pediatr Adolesc Med 1994: 148:141-146.
- Blair PS, Fleming PJ, Bensley D, et al. Smoking and the sudden infant death syndrome: results from 1993-5 case-control study for confidential inquiry into stillbirths and deaths [in] infancy. Br Med J 1996;313:195-198.
- Mitchell EA, Scragg R. Observations on ethnic differences in SIDS mortality in New Zealand. Early Hum Dev 1994; 38: 151-157.
- American Academy of Pediatrics Task Force on Infant Positioning and SIDS. Pediatrics 1996; 98:1216-1218.
- Gershon NB, Moon RY. Infant sleep position in licensed child care centers. Pediatrics 1997; 100:75-78.
- MacDorman MF, Cnattingius S, Hoffman HJ, et al. Sudden infant death syndrome and smoking in the United States and Sweden. Am J Epidemiol 1997; 146(3):249-257.
- Mitchell EA, Tuohy PG, Brunt JM, et al. Risk factors for sudden infant death syndrome following the prevention campaign in New Zealand: a prospective study. Pediatrics 1997; 100:835-840.
- Center for Health Statistics, Oregon Health Services. Oregon Vital Statistics County Data 1996, April 1998; 13.