Sudden Infant Death Syndrome Research Today is a free monthly online journal that collates and summarizes the latest research about Sudden Infant Death Syndrome, including details on sids, causes, prevention, statistics. | ||||||||
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Sudden infant death syndrome (SIDS) is a syndrome marked by the symptoms of sudden and unexplained death of an apparently healthy infant aged one month to one year. The term cot death is often used in the United Kingdom, Australia and New Zealand, while crib death is sometimes used in North America. OverviewTypically the infant is found dead after having been put to bed, and exhibits no signs of having suffered.[1] SIDS is a diagnosis of exclusion. It can only be applied to an infant whose death is sudden and unexpected, and remains unexplained after the performance of an adequate postmortem investigation including
SIDS is responsible for roughly 1 death per 2,000 births in the U.S. It is responsible for far fewer deaths than congenital disorders and disorders related to short gestation, though it is the leading cause of death in healthy babies after one month of age. According to the American SIDS Institute, SIDS is "a tragedy which leaves [parents] with a sadness and a feeling of vulnerability that lasts throughout their lives." [2] In November 2007, the Bill & Melinda Gates foundation contributed $11 million to distribute 200,000 cribs in the United States of America to families at-risk of SIDS or in need of financial assistance. Additionally, the grant will fund a study of infant mortality over 100,000 families. The hypothesis of the study is that availability of safe cribs and knowledge of safe sleep practices will reduce the occurrence of SIDS. [3] Undiagnosed conditionsSome conditions that may be undiagnosed and thus result in a diagnosis of SIDS include
Risk factorsVery little is certain about the possible causes of SIDS, and there is no proven method for prevention. Although studies have identified risk factors for SIDS, such as putting infants to bed on their stomachs, there has been little understanding of the syndrome's biological cause or causes. The frequency of SIDS appears to be a strong function of infant sex and the age, ethnicity, and the education and socio-economic status of the parents. According to a study published in October 2007 in the Journal of the American Medical Association, babies who die of SIDS have abnormalities in the part of the brain called the Medulla which helps control functions like breathing, blood pressure and arousal. Researchers examined the brains of 31 babies who had died of SIDS and 10 who had died from other causes. It was discovered that the Medulla had neurons that released a chemical called serotonin. The number of these neurons was greater than normal in 55% of the brains of the babies who had died of SIDS. They also found that babies had fewer receptors for serotonin and that abnormalities in the brain stem appear to affect the ability to use and recycle serotonin, which is responsible for regulating mood as well as vital body functions. According to the National Institutes of Health, which funded the study, the new finding is the strongest evidence to date suggesting that innate differences in a specific part of the brain may place some at increased risk of dying from SIDS.[4] In a British study released May 29, 2008 researchers discovered that the common bacterial infections Staphylococcus aureus (staph) and Escherichia coli (E. coli) appear to be the cause of some cases of Sudden Infant Death Syndrome. Both the "staph" and E. coli bacteria had a greater presence in the unexplained deaths of infants.[5] SIDS cases peak between the ages of 8- 10 weeks of age, which is also the time frame in which the antibodies that were passed along from mother to child are starting to disappear and babies have not yet made their own antibodies. Listed below are several factors associated with increased probability of the syndrome based on information available prior to this recent study. Prenatal risks
Post-natal risks
Risk reduction for SIDSThough SIDS cannot be prevented, parents of infants are encouraged to take several precautions in order to reduce the likelihood of SIDS. EnvironmentSleep positioningSleeping on the back has been recommended by (among others) the American Academy of Pediatrics (starting in 1992) to avoid SIDS, with the catchphrase "Back To Bed" and "Back to Sleep." The incidence of SIDS has fallen sharply in a number of countries in which the back to bed recommendation has been widely adopted, such as the US and New Zealand.[10] However, the absolute incidence of SIDS prior to the Back to Sleep Campaign was already low in the US.[citation needed] Among the theories supporting the Back to Sleep recommendation is the idea that small infants with little or no control of their heads may, while face down, inhale their exhaled breath (high in carbon dioxide) or smother themselves on their bedding -- the brain-stem anomaly research (above) suggests that babies with that particular genetic makeup do not react "normally" by moving away from the pooled CO2, and thus smother. Another theory[citation needed] is that babies sleep more soundly when placed on their stomachs, and are unable to rouse themselves when they have an incidence of sleep apnea, which is thought to be common in infants. Arguments against infant back-sleeping include concerns that an infant could choke on fluids it brings up.[11] Hospital staff commonly place newborns on their side, although they advise parents to place their infants on their backs after going home from the hospital.[citation needed] Other concerns raised about the Back to Sleep Campaign have included the possible increase the risk of positional facial and head deformities (see positional plagiocephaly),[12] possible interference with development of good sleep habits (which in turn may have other bad effects),[13] and possible interference with motor skills development (as infants delay attempts to lift their heads, crawl, etc.)[14]. BreastfeedingA 2003 study published in Pediatrics, which investigated racial disparities in infant mortality in Chicago, found that previously or currently breastfeeding infants in the study had 1/5 the rate of SIDS as non-breastfed infants, but that "it became nonsignificant in the multivariate model that included the other environmental factors. These results are consistent with most published reports and suggest that other factors associated with breastfeeding, rather than breastfeeding itself, are protective."[15] Co-sleepingA controversial approach to lowering SIDS rates is limiting co-sleeping. A 2005 policy statement by the American Academy of Pediatrics on sleep environment and the risk of SIDS condemned all co-sleeping and bedsharing as unsafe. However, some data[16] has suggested that almost all SIDS deaths in adult beds occur when other prevention methods, such as placing infants on their backs, are not used. Secondhand smoke reductionAccording to the U.S. Surgeon General’s Report, secondhand smoke is connected to SIDS.[17] Infants who die from SIDS tend to have higher concentrations of nicotine and cotinine (a biological marker for secondhand smoke exposure) in their lungs than those who die from other causes. Infants exposed to secondhand smoke after birth are also at a greater risk of SIDS. Parents who smoke can significantly reduce their children's risk of SIDS by either quitting or smoking only outside and leaving their house completely smoke-free. Sleeping areaBeddingTo prevent SIDS, many families use firm mattresses with tight-fitting sheets in cribs or bassinets. The families do not allow pillows, stuffed animals, or fluffy bedding in the cribs. In cold weather, the families dress the infants warmly in well-fitted clothing.[18]. The infants blankets should also not be placed over their heads. It has been recommended that the infants are only covered up to their chest with their arms exposed. This will help eliminate the chances of the infant moving the blanket over their heads. Sleep sacksIn colder environments where bedding is required to maintain a baby's body temperature, the use of a sleep sack is becoming more popular. A study published in the European Journal of Pediatrics in August 1998[19] has shown the protective effects of a sleep sack as reducing the incidence of turning from back to front during sleep, reinforcing putting a baby to sleep on their back for placement into the sleep sack and preventing bedding from coming up over the face which leads to increased temperature and carbon dioxide rebreathing. They conclude in their study "The use of a sleeping-sack should be particularly promoted for infants with a low birth weight." PacifiersA 2005 study indicated that use of a pacifier is associated with a 90% reduction in the risk of SIDS.[20] It has been speculated that the raised surface of the pacifier holds the infant's face away from the mattress, reducing the risk of suffocation. Although suffocation is an actual cause, while SIDS refers to an unexplained infant death, in the absence of sufficient postmortem investigation, a SIDS diagnosis may result. Bumper padsBumper pads may be a contributing factor in SIDS deaths and should be removed. Health Canada, the Canadian government's health department, issued an advisory[21] recommending against the use of bumper pads, with the warning that they may decrease the amount of oxygen rich air available to the baby:
Speculated associationsA number of theoretical causes have been proposed as a trigger for SIDS, but many of them are unproven or have not been thoroughly studied and peer-reviewed. Mattress bugsA 2002 study hypothesized that bugs feeding on baby vomit and dust could be fatal for small children, creating 'supertoxins' which spur the baby's body into overreacting, leading to anaphylactic shock.[22] Brain disorderA recently published research article in the Journal of the American Medical Association showed evidence that cells in the brainstem fail to develop receptors for Serotonin in the womb. This abnormality continues until after birth, supposedly until the end of their first year. This would account for there being few to no SIDS deaths after the first year of infancy and the reason the risk is more for premature infants. The SIDS Alliance/First Candle has posted a message about this along with a link to the abstract on their website (www.firstcandle.com), which can be accessed from the front page. Vitamin CAccording to a 1993 article in Journal of Orthomolecular Medicine, Australian medical doctor Archie Kalokerinos performed research showing that high doses of vitamin C eliminates SIDS.[23] As SIDS was shown to be caused solely by vitamin deficiency, the article stated that it was no longer a syndrome, and that the proper disease name is now SID. As of January 2007, the Journal of Orthomolecular Medicine was not included among journals selected by the U.S. National Library of Medicine for inclusion in their Medline database.[24][25] Toxic gasesIn 1989, a controversial piece of research by UK Scientist Barry Richardson claimed that all cot deaths were the result of toxic nerve gases being produced through the action of fungus in mattresses on compounds of phosphorus, arsenic and antimony. These chemicals are frequently used to make mattresses fire-retardant. A major plank in this explanation is the widely-observed phenomenon that the risk of cot death rises from one sibling to the next. Richardson claims that the cause is that parents are more likely to buy new bedding for their first child, and to re-use that bedding for later children. The more frequently used the bedding is, the more chance there will be that fungus has become resident in the material; thus, a higher chance of cot death. A paper by Peter Fleming and Peter Blair [4] references evidence from other studies that both supports and refutes the increasing occurrence of SIDS with mattress sharing and suggests that this is still inconclusive. In 1994, the New Zealand government, under the advice of Dr. Jim Sprott, issued advice recommending new parents to either buy bedding free of the toxic compounds or to wrap the mattresses in a barrier film to prevent the escape of the gases. Dr. Sprott claims that no case of cot death has ever been traced back to a properly manufactured or wrapped mattress [5]. However, a final report of The Expert Group to Investigate Cot Death Theories: Toxic Gas Hypothesis, published in May 1998, concluded that "there was no evidence to substantiate the toxic gas hypothesis that antimony- and phosphorus-containing compounds used as fire retardants in PVC and other cot mattress materials are a cause of SIDS. Neither was there any evidence to believe that these chemicals could pose any other health risk to infants."[26] The report also states that "in normal cot-like conditions it is not possible to generate toxic gas from antimony in mattresses" and "babies have also been found to die on wrapped mattresses." Dr. Sprott's website, however, claims [6] [7] that the study does not actually refute his theory:
According to Dr. Sprott, as of 2006, the New Zealand government has not reported any SIDS deaths when babies have slept on mattresses wrapped according to his method. While the Limerick report claims that babies have been found to die on wrapped mattresses, Dr. Sprott argues that a chemical analysis of the bedding should be performed. He additionally claims that this part of the report was flawed:
Central Respiratory Pattern DeficiencyThere is ongoing research in the pediatric/neonatal community that has begun to associate apnea-like breathing cessations in animal models with unusual neural architecture or signal transduction in central pattern generator circuits including the pre-Bötzinger complex.[28] It is possible that irregularities in neurotransmitter release (such as GABA, adenosine, and NMDA) or deficiencies in their associated receptors (including both GABAA, GABAB subtypes and NMDA-glutamate receptors) are linked to incomplete prenatal development as is evident in pre-term infants. Genetic factors are also being studied with several rat and mouse knockouts. Upper cervical spinal cord injury as a result of birth traumaDuring birth, if the infant's head is traumatically turned side to side, upper cervical spinal injury can result. Difficulty breathing is a classic sign of upper spinal cord and brain-stem injury. [29] When infants with undiagnosed upper cervical spinal cord injury are continually placed on their stomach for sleep, they are forced to turn their head to the side to breathe. This is hypothesised to aggravate and prolong the spinal cord injury sustained during birth, preventing proper healing and ultimately leading to fatal breathing difficulty. GenderThere is a consistent 50% male excess in SIDS per 1000 live births of each sex. Given a 5% male excess birth rate (105 male to 100 female live births) there appear to be 3.15 male SIDS per 2 female SIDS for a male fraction of 0.61.[30][31] The X-linkage hypotheses for SIDS and the male excess in infant mortality have shown that the 50% male excess could be caused by a dominant X-linked allele that occurs with a frequency of ⅓ that is protective of transient cerebral anoxia. An unprotected XY male would occur with a frequency of ⅔ and an unprotected XX female would occur with a frequency of 4⁄9. The ratio of ⅔ to 4⁄9 is 1.5 to 1 which matches the observed male 50% excess rate of SIDS. Although many authors have found autosomal and mitochondrial genetic risk factors for SIDS they cannot explain the male excess because such gene loci have the same frequencies for males and females. Supporting evidence is found by examination of other causes of infant respiratory death, such as inhalation of food and other foreign objects. Although food is prepared identically for male and female infants, there is a 50% male excess of death from such causes indicating that males are more susceptible to the cerebral anoxia created by such incidents in exactly the same proportion as found in SIDS. See the data found at http://wonder.cdc.gov for 9ICD 911 and 912 death rates by sex. The study which indicated that there was a relationship between fewer serotonin binding sites and SIDS noted that the boys "had significantly fewer serotonin binding sites than girls". SIDS and child abuseBritish former pediatrician Roy Meadow believes that many cases diagnosed as SIDS are really the result of child abuse on the part of a parent displaying Munchausen Syndrome by Proxy (a condition which he was first to describe, in 1977). During the 1990s and early 2000s, a number of mothers of multiple apparent SIDS victims were convicted of murder, to varying degrees on the basis of Meadow's opinion. In 2003 a number of high-profile acquittals brought Sir Meadow's theories into disrepute, and many now doubt their credibility. Several hundred murder convictions were reviewed, leading to several high-profile cases being re-opened and convictions overturned. The Royal Statistical Society issued a media release refuting the expert testimony in one UK case in which the conviction was subsequently overturned.[32] The New York Times covered The Death of Innocents: A True Story of Murder, Medicine and High-Stakes Science in 1997[33], stating
Nitrogen dioxideA 2005 study by researchers at the University of California, San Diego found that "SIDS may be related to high levels of acute outdoor NO2 exposure during the last day of life."[34] While nitrogen dioxide (NO2) exposure may be one of many possible risk factors, it is not considered causal, and the report cautioned that further studies were needed to replicate the result. VaccinationThe relationship between vaccinations and SIDS has been well studied. Babies that are vaccinated are possibly protected from SIDS according to one study in the British Medical Journal.[35] Other studies[36][37] indicate that there is no significant difference in risk. Inner Ear DamageRecords of hearing tests administered to certain infants show that those who later died of SIDS had a unique pattern of partial hearing loss, according to the journal Early Human Development.[38] One suggestion for the cause of SIDS is that the deaths are caused by disturbances in respiratory control (from other than suffocation). The vestibular apparatus of the inner ear has been shown to play an important role in respiratory control during sleep. It is speculated that this inner ear damage could be linked to SIDS. It is speculated that the damage occurs during delivery, particularly when prolonged contractions create greater blood pressure in the placenta. The right ear is directly in the "line of fire" for blood entering the fetus from the placenta, and thus could be most susceptible to damage. If the findings are relevant, it may be possible to take corrective measures. Researchers are beginning animal studies to explore the connection.[citation needed] Side Effects of SIDS Risk Reduction RecommendationsDr. Rafael Pelayo from Stanford University and a number of other pediatric sleep researchers in the U.S. have stated that they believe that the American Academy of Pediatics recommendations regarding cosleeping and pacifier use may have unintended consequences. They have stated that the SIDS prevention strategy of the American Academy of Pediatrics which keeps infants at a low arousal threshold and reduces the time in quiet sleep may be unhealthy for children. They state that slow wave sleep is the most restorative form of sleep and limiting this sleep in the first 12 months of life may have unintended consequences to both the sleep and the infant [39]. According to a 1998 study by British researchers that compared back sleeping infants to stomach sleeping infants there were developmental differences at 6 months of age between the two groups. At 6 months of age the stomach sleeping infants had higher gross motor scores, social skills scores, and total development skills scores than the back sleeping infants. The differences were apparent at the 5% statistical significant level. But, at 18 months the differences were no longer apparent. The researchers deemed the lower development scores of back sleeping infants at 6 months of age to be transient and stated that they do not believe the back sleeping recommendations should be changed.[40]. Other scientists have stated that the conclusion that the negative effects of back sleep at 18 months of age is transient is based upon very little evidence and that no long-term randomized trials have been completed [41]. Other side effects of the back sleeping position include increased rates of shoulder retraction, positional plagiocephaly, and positional torticollis.[42]. Some scientists dispute that plagiocephaly is a negative side effect. Dr. Peter Fleming, who is co-author of the study that deemed delays at 6 months of age to be transient, has stated that he does not think plagiocephaly is a negative side effect of back sleep. In an interview with the Guardian Dr. Fleming stated "I do not think it is a medical problem - it is more of a cosmetic one. Mothers may feel it is a syndrome and a problem when it really is nonsense." [43] A research study on children with plagiocephaly found that 26% had mild to severe psychomotor delay. This study also showed that 10% of infants with plagiocephaly had mild to severe mental development delay [44]. Because of the delays caused by back sleep some medical professionals have suggested that the "normal" ages at which children had previously attained developmental milestones should be pushed back. This would enable medical professionals to consider "normal" children who previously were considered developmentally delayed [45]. Further reading
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External links
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