SIDS has been defined as the abrupt and unexplained death of an apparently healthy infant under one year of age, remaining unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history.
(Expert Panel of the National Institute of Child Health and Human Development in PediatricPathology, v.11, no.5, Sept-Oct 1991, p.681)
There have been several papers published recently on risk factors associated with sudden infant death syndrome especially the prone sleeping position and cigarette smoke .
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.
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 July,96 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."
* 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.
* 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."
* * * 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.
In the March 8, 95 Journal Of The American Medical Association Hillary Sandra Klonoff- Cohen and her colleagues at the University of California, San Diego report breathing cigarette smoke to be important risk factor associated with SIDS.
Infants breathing the smoke of others in the same house were found to be 3 1/2 times more likely to die of SIDS than the youngsters not exposed to smoke in their homes. Researchers suggest cigarette smoke .may impair the control of children's breathing.
The scientists interviewed 200 parents of children under age 1 who died of SIDS and 200 parents of healthy babies who were similar to the SIDS victims in age, race, and other characteristics. Most children who die of SIDS are 2 to 4 months old. The team found that while two thirds of all infants slept prone, 80 percent of all SIDS victims were prone when they died.
New data may convince more doctors to warn of the dangers of infants sleeping prone
Marian Willinger of the National Institutes of Health in Bethesda, Md., recommends keeping babies away from smoke as much as possible and off their stomachs when sleeping.
(In a separate recent study published in the April 95 Journal of Family Practice researchers have found that mothers in the United States who smoke may cause the deaths of almost 6000 babies and over 115,000 miscarriages every year. Smoking was also found to be associated with 55,000 cases of low birth weight.)
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
References: 1. Klonoff-Cohen HS; Edelstein SL; Lefkowitz ES; Srinivasan IP; Kaegi D; Chang JC; Wiley KJ.
The effect of passive smoking and tobacco exposure through breast milk on sudden infant death syndrome .
Jama, 1995 Mar 8, 273(10):795-8.
(UI: 95165594)
Abstract: OBJECTIVE. To examine the relationship between sudden infant death syndrome (SIDS) and smoking during pregnancy; postnatal tobacco smoke exposure from the mother, father, live-in-adults, and day care providers; and postnatal smoke exposure from breast-feeding. DESIGN. Case-control study. SETTING. Five counties in Southern California. PARTICIPANTS. A total of 200 white, African-American, Hispanic, and Asian parents of infants who died of SIDS between 1989 and 1992 were compared with 200 control parents who delivered healthy infants. Case infants were matched to control infants on the basis of birth hospital, birth date, gender, and race. All information was obtained from a detailed telephone interview and validated with medical records. MAIN OUTCOME MEASURES. Risk of SIDS associated with passive smoking by the mother, father, live-in adults, and day care providers; smoking in the same room as the infant; total number of cigarettes smoked by all adults; and maternal smoking during the time period of breast-feeding. RESULTS. Conditional logistic regression resulted in overall adjusted odds ratios (ORs) for SIDS associated with passive smoke from the mother of 2.28, the father of 3.46, other live-in adults of 2.18, and all sources of 3.50 (95% confidence interval, 1.81 to 6.75), while simultaneously adjusting for birth weight, sleep position, prenatal care, medical conditions at birth, breast-feeding, and maternal smoking during pregnancy. A dose-response effect was noted for SIDS associated with increasing numbers of cigarettes, as well as total number of smokers. Breast-feeding was protective for SIDS among nonsmokers (OR = 0.37) but not smokers (OR = 1.38), when adjusting for potential confounders. CONCLUSIONS. Passive smoking in the same room as the infant increases the risk for SIDS. Physicians should educate new and prospective parents about the risk of tobacco smoke exposure during pregnancy and the first year of the infant's life.
2.. Dwyer T; Ponsonby AL; Blizzard L; Newman NM; Cochrane JA.
The contribution of changes in the prevalence of prone sleeping position to the decline in sudden infant death syndrome in Tasmania.
Jama, 1995 Mar 8, 273(10):783-9.
(UI: 95165592)
Abstract: OBJECTIVE. To determine the independent contribution of changes in nfant sleep position to the recent decline in sudden infant death syndrome SIDS) rate in Tasmania. DESIGN. (1) A comparison of the whole population ncidence of SIDS before and after an intervention to reduce the prevalence of prone sleeping position. (2) A within-cohort analysis of the contribution of sleep position and other exposures to the decline in SIDS after the intervention. SETTING. Tasmania, Australia. PARTICIPANTS. (1) All SIDS cases from 1975 through 1992. (2) A sample of one in five infants born n Tasmania who at perinatal assessment were scored to be at higher risk or SIDS since January 1988. Of 5534 infants included in the study, 39 ater died of SIDS. INTERVENTIONS. Multiple public health activities to educe the prevalence of the prone infant sleeping position in Tasmania and verbal information on the association between prone position and SIDS to cohort participants from May 1, 1991. MAIN OUTCOME MEASURE. Sudden infant death syndrome incidence. RESULTS. The Tasmanian SIDS rate decreased (P < 01) from 3.8 (95% confidence interval [CI], 3.5 to 4.2) deaths per 1000 ive births from 1975 through 1990 to a rate of 1.5 (95% CI, 0.9 to 2.2) deaths per 1000 live births in 1991 through 1992. The SIDS mortality rate n the cohort by period of birth was 7.6 (95% CI, 4.9 to 10.3) deaths per 1000 live births for those born from May 1, 1988, through April 30, 1991, and 4.1 (95% CI, 1.3 to 7.0) deaths per 1000 infants for those born from May 1, 1991, through October 31, 1992. The prevalence of usual prone leeping position at 1 month of age was 29.9% and 4.3% in these two cohorts, respectively (adjusted odds ratio, 0.11; 95% CI, 0.08 to 0.13). Logistic regression demonstrated that 70% of the SIDS rate reduction in the cohort could be accounted for by the decreased prevalence of the prone leeping position. Other factors examined individually contributed to less han 10% of the SIDS rate reduction. CONCLUSIONS. The major contributing actor to the recent SIDS rate decline in Tasmania has been the reduction n the proportion of infants usually sleeping prone.
See Also:
1) Farooqi S.
Ethnic differences in infant care practices and in the incidence of sudden infant death syndrome in Birmingham.
Early Human Development, 1994 Sep 15, 38(3):209-13.
(UI: 95121256)
Abstract: Certain infant care practices have consistently been shown to play an important role in the aetiology of the sudden infant death syndrome (SIDS).In the UK, the incidence of SIDS amongst Asians is less than half that of whites. We conducted a questionnaire- based survey of 374 multiparous mothers from a multiracial community in Birmingham. We found that themajority of Asian infants slept in the parental bedroom at night, 94%compared to 61% of whites, whilst 33% of white infants slept alone comparedto 4% of Asians. Three times as many white mothers as Asians placed infants prone (31% vs. 11%). We, therefore, observed marked differences in theinfant care practices of Asians compared to whites in the UK, which may partly account for the low incidence of SIDS amongst infants of Asianorigin.
2)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 May, 93(5):814-9.
(UI: 94218189)
Pub type: Consensus Development Conference; Consensus Development
Conference, NIH; Journal Article; Review.
Abstract: OBJECTIVE. To evaluate the current knowledge on the relationshipbetween infant sleep position and sudden infant death syndrome (SIDS), andto determine how the information can be used to guide further activities inthe United States. METHODS. Data from international vital statistics,epidemiologic studies of SIDS risk factors, and studies of outcomes ofpublic health interventions that advocated nonprone sleeping to reduce therisk for SIDS were discussed at a meeting held by the National Institute ofChild Health and Human Development (NICHD) with cosponsorship from theNational Institute on Deafness and Other Communication Disorders (NIDCD),and the National Center for Health Statistics (NCHS) on January 13, and 14,1994. RESULTS. Trends in postneonatal mortality and SIDS rates from 1980through 1992 were evaluated for Australia, Britain, New Zealand, theNetherlands, Norway, Sweden, and the United States. All of the countries that experienced a rapid decline in prone sleeping also had reductions ofapproximately 50% in their SIDS rates. Postneonatal mortality rates droppedas well, with the reduction in SIDS being the primary contributor to thereported declines. The major behavioral change in all targeted populationswas in sleep position. No significant changes were observed in theproportion of parents who smoked cigarettes, or in breast- feeding.Preliminary data from population-based studies showed there were noreported adverse outcomes associated with a change to side or back sleepposition, such as an increase in deaths due to aspiration or in apparentlife-threatening events. CONCLUSION. The overwhelming opinion of theassembled experts was that the evidence justified greater effort to reachparents with the American Academy of Pediatrics' recommendation thathealthy infants, when being put down to sleep, be positioned on their sideor back.
3) Milerad J; Rajs J; Gidlund E.
Nicotine and cotinine levels in pericardial fluid in victims of SIDS.
Acta Paediatrica, 1994 Jan, 83(1):59-62.
(UI: 94251048)
Abstract: We have analyzed the levels of nicotine and cotinine in pericardialfluid in 24 consecutively autopsied cases of sudden unexpected death ininfants aged one to six months. Our aim was to determine to what extentvictims of sudden infant death may have been exposed to passive smokingnear the time of death. Sixteen of the decreased infants were classified asSIDS at autopsy. Other contributing causes of death, predominantlyinfections, were found in eight cases. Eight infants (30%) had cotininelevels less than 2 ng, indicating that no significant exposure to nicotinehad occurred near the time of death. Of the remaining 70%, five had beenmoderately exposed, seven markedly exposed and four heavily exposed(cotinine levels 2-10 ng, 10-50 ng and more than 50 ng, respectively).Since only 18% of Swedish women smoke after childbearing we conclude thatnicotine exposure in infants who died suddenly was much higher than onewould otherwise expect. It is hypothesized that high concentrations ofnicotine and nicotine metabolites around the heart may affect cardiacfunction and thus play a role in the mechanisms causing SIDS or othercategories of sudden unexpected death.