SIDS
Sudden infant death syndrome, sometimes known as cot death or crib death, is the sudden unexplained death of a child of less than one year of age. Diagnosis requires that the death remain unexplained even after a thorough autopsy and detailed death scene investigation. SIDS usually occurs between the hours of midnight and 9:00 a.m., or when the baby is sleeping. There is usually no noise or evidence of struggle. SIDS remains one of the leading causes of infant mortality in Western countries, constituting almost 1/3 of all post-neonatal deaths.
The exact cause of SIDS is unknown. The requirement of a combination of factors including a specific underlying susceptibility, a specific time in development, and an environmental stressor has been proposed. These environmental stressors may include sleeping on the stomach or side, overheating, and exposure to tobacco smoke. Accidental suffocation from bed sharing or soft objects may also play a role. Another risk factor is being born before 37 weeks of gestation. Between 1% and 5% of SIDS cases are estimated to be misidentified infanticides caused by intentional suffocation. SIDS makes up about 80% of sudden and unexpected infant deaths. The other 20% of cases are often caused by infections, genetic disorders, and heart problems.
The most effective method of reducing the risk of SIDS is putting a child less than one year old on their back to sleep. Other measures include a firm mattress separate from but close to caregivers, no loose bedding, a relatively cool sleeping environment, using a pacifier, and avoiding exposure to tobacco smoke. Breastfeeding and immunization may also be preventative. Measures not shown to be useful include positioning devices and baby monitors. Evidence is not sufficient for the use of fans. Grief support for families affected by SIDS is important, as the death of the infant is unexpected, unexplained, and can cause suspicion that the infant may have been intentionally harmed.
Rates of SIDS vary nearly tenfold in developed countries from one in a thousand to one in ten thousand. Globally, it resulted in about 19,200 deaths in 2015, down from 22,000 deaths in 1990. SIDS was the third leading cause of death in children less than one year old in the United States in 2011. It is the most common cause of death between one month and one year of age. About 90% of cases happen before six months of age, with it being most frequent between two months and four months of age. It is more common in boys than girls. Rates of SIDS have decreased by up to 80% in areas with "Safe to Sleep" campaigns.
Definition
The syndrome applies only to infants under one year of age. SIDS is a diagnosis of exclusion and should be applied to only those cases in which an infant's death is sudden and unexpected, and remains unexplained after the performance of an adequate postmortem investigation, including:- an autopsy ;
- investigation of the death scene and circumstances of the death; and
- exploration of the medical history of the infant and family.
Australia and New Zealand shifted to sudden unexpected death in infancy for professional, scientific, and coronial clarity:
In addition, the US Centers for Disease Control and Prevention have proposed that such deaths be called sudden unexpected infant deaths and that SIDS is a subset of SUID.
Age
SIDS has a four-parameter lognormal age distribution that spares infants shortly after birth—the time of maximal risk for almost all other causes of non-trauma infant death.By definition, SIDS deaths occur under the age of one year, with the peak incidence occurring when the infant is two to four months old. This is considered a critical period because the infant's ability to rouse from sleep is not yet mature.
Risk factors
The exact cause of SIDS is unknown. Although studies have identified risk factors for SIDS, such as putting infants to bed on their bellies, there has been little understanding of the syndrome's biological process or its potential causes. Deaths from SIDS are unlikely to be due to a single cause, but rather to multiple risk factors. The frequency of SIDS does appear to be influenced by social, economic, or cultural factors, such as maternal education, race or ethnicity, or poverty. SIDS is believed to occur when an infant with an underlying biological vulnerability, who is at a critical development age, is exposed to an external trigger. The following risk factors generally contribute either to the underlying biological vulnerability or represent an external trigger:Tobacco smoke
SIDS rates are higher in babies of mothers who smoke during pregnancy. Between no smoking and smoking one cigarette a day, on average, the risk doubles. About 22% of SIDS in the United States is related to maternal smoking. SIDS correlates with levels of nicotine and its derivatives in the baby. Nicotine and derivatives cause alterations in neurodevelopment.Sleeping
Placing an infant to sleep while lying on the belly or side rather than on the back increases the risk for SIDS. This increased risk is greatest at two to three months of age. Elevated or reduced room temperature also increases the risk, as does excessive bedding, clothing, soft sleep surfaces, and stuffed animals in the bed. Bumper pads may increase the risk of SIDS due to the risk of suffocation. They are not recommended for children under one year of age, as this risk of suffocation greatly outweighs the risk of head bumping or limbs getting stuck in the bars of the crib.Sharing a bed with parents or siblings also increases the risk for SIDS. This risk is greatest in the first three months of life, when the mattress is soft, when one or more persons share the infant's bed, especially when the bed partners are using drugs or alcohol or are smoking. The risk remains, however, even in parents who do not smoke or use drugs. The American Academy of Pediatrics thus recommends "room-sharing without bed-sharing", stating that such an arrangement can decrease the risk of SIDS by up to 50%. Furthermore, the academy has recommended against devices marketed to make bed-sharing "safe", such as "in-bed co-sleepers".
Room sharing as opposed to solitary sleeping is known to decrease the risk of SIDS.
Breastfeeding
is associated with a lower risk of SIDS. It is not clear if co-sleeping among mothers who breastfeed without any other risk factors increases SIDS risk.Pregnancy and infant factors
SIDS rates decrease with increasing maternal age, with teenage mothers at greatest risk. Delayed or inadequate prenatal care also increases risk. Low birth weight is a significant risk factor. In the United States from 1995 to 1998, the SIDS death rate for infants weighing 1000–1499 g was 2.89/1000, while for a birth weight of 3500–3999 g, it was only 0.51/1000. Premature birth increases the risk of SIDS death roughly fourfold. From 1995 to 1998, the US SIDS rate for births at 37–39 weeks of gestation was 0.73/1000, while the SIDS rate for births at 28–31 weeks of gestation was 2.39/1000.Anemia has also been linked to SIDS. SIDS incidence rises from zero at birth, is highest from two to four months of age, and declines toward zero after the infant's first year.
Genetics
plays a role, as SIDS is more prevalent in males. There is a consistent 50% male excess in SIDS per 1000 live births of each sex. Given a 5% male excess birth rate, there appears to be 3.15 male SIDS cases per 2 female cases, for a male fraction of 0.61. This value of 61% in the US is an average of 57% black male SIDS, 62.2% white male SIDS, and 59.4% for all other races combined. Note that when multiracial parentage is involved, the infant's race is arbitrarily assigned to one category or the other; most often, it is chosen by the mother. The X-linkage hypothesis for SIDS and the male excess in infant mortality have shown that the 50% male excess might be related to a dominant X-linked allele, occurring with a frequency of that is protective against transient cerebral anoxia. An unprotected male would occur with a frequency of and an unprotected female would occur with a frequency of.About 10 to 20% of SIDS cases are believed to be due to channelopathies, which are inherited defects in the ion channels that play an important role in the contraction of the heart.
Genetic evidence published in November 2020 concerning the case of Kathleen Folbigg, who was imprisoned for the death of her children, showed that at least two of the children had genetic mutations in the CALM2 gene that predisposed them to heart complications. Kathleen was pardoned 5 June 2023 after spending 20 years in jail.
Alcohol
Drinking of alcohol by parents is linked to SIDS. One study found a positive correlation between the two during New Year celebrations and weekends. Another found that alcohol use disorder was linked to a more than doubling of risk.Other
A 2022 study found that infants who died of SIDS exhibited significantly lower specific activity of butyrylcholinesterase, an enzyme involved in the brain's arousal pathway, shortly after birth. This can serve as a biomarker to identify infants with a potential autonomic cholinergic dysfunction and elevated risk for SIDS.SIDS has been linked to cold weather, with this association believed to be due to over-bundling and thus, overheating. Premature babies are at four times the risk of SIDS, possibly related to an underdeveloped ability to automatically control the cardiovascular system.
A 2-part edition of The Cook Report from 1994 claimed that antimony- and phosphorus-containing compounds used as fire retardants in PVC and other cot mattress materials were a cause of SIDS. Subsequent investigation by an Expert Panel led by Lady Limerick found that there was no evidence to support this claim. The report also states that toxic gas cannot be generated from antimony in mattresses and that babies had SIDS on mattresses that did not contain the compound.
It has been suggested that some cases of SIDS may be related to Staphylococcus aureus and Escherichia coli infections.