Sudden infant death syndrome
Sudden infant death syndrome (SIDS), also 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 during sleep. Typically death occurs between the hours of 00:00 and 09:00. There is usually no noise or evidence of struggle.SIDS remains the leading cause of infant mortality in Western countries, contributing to half of all post-neonatal deaths.
The exact cause of SIDS is unknown.[3] The requirement of a combination of factors including a specific underlying susceptibility, a specific time in development, and an environmental stressor has been proposed.[2][3] These environmental stressors may include sleeping on the stomach or side, overheating, and exposure to tobacco smoke.[3] Accidental suffocation from bed sharing (also known as co-sleeping) or soft objects may also play a role.[2][11] Another risk factor is being born before 39 weeks of gestation.[7] SIDS makes up about 80% of sudden and unexpected infant deaths (SUIDs).[2] The other 20% of cases are often caused by infections, genetic disorders, and heart problems.[2] While child abuse in the form of intentional suffocation may be misdiagnosed as SIDS, this is believed to make up less than 5% of cases.[2]
The most effective method of reducing the risk of SIDS is putting a child less than one year old on their back to sleep.[7] 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.[5]Breastfeeding and immunization may also be preventive.[5][6] Measures not shown to be useful include positioning devices and baby monitors.[5][6] Evidence is not sufficient for the use of fans.[5] Grief support for families affected by SIDS is important, as the death of the infant is sudden, without witnesses, and often associated with an investigation.[2]
Rates of SIDS vary nearly tenfold in developed countries from one in a thousand to one in ten thousand.[2][12] Globally, it resulted in about 19,200 deaths in 2015, down from 22,000 deaths in 1990.[13][14] SIDS was the third leading cause of death in children less than one year old in the United States in 2011.[15] It is the most common cause of death between one month and one year of age.[7] About 90% of cases happen before six months of age, with it being most frequent between two months and four months of age.[2][7] It is more common in boys than girls.[7] Rates have decreased in areas with "safe sleep campaigns" by up to 80%.[12]
Video explanation
Definition
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 (by an experienced pediatric pathologist, if possible);
- investigation of the death scene and circumstances of the death; and
- exploration of the medical history of the infant and family.
After investigation, some of these infant deaths are found to be caused by suffocation, hyperthermia or hypothermia, neglect or some other defined cause.[16]
Australia and New Zealand are shifting to the term "sudden unexpected death in infancy" (SUDI) for professional, scientific, and coronial clarity.
The term SUDI is now often used instead of sudden infant death syndrome (SIDS) because some coroners prefer to use the term 'undetermined' for a death previously considered to be SIDS. This change is causing diagnostic shift in the mortality data.[17]
In addition, the U.S. Centers for Disease Control and Prevention (CDC) has recently proposed that such deaths be called "sudden unexpected infant deaths" (SUID) and that SIDS is a subset of SUID.[18]
Age
SIDS has a 4-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 at 2 to 4 months of age. This is considered a critical period because the infant's ability to rouse from sleep is not yet mature.[2]
Risk factors
The cause of SIDS is unknown.[3] 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 process or its potential causes. Deaths from SIDS are unlikely to be due to a single cause, but rather multiple risk factors.[19] The frequency of SIDS does appear to be influenced by social, economic, and cultural factors, such as maternal education, race or ethnicity, and poverty.[20] 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.[2] 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.[21][22] Between no smoking and smoking 1 cigarette a day, on average, the risk doubles. About 22% of SIDS in the United States is related to mother's smoking.[23] SIDS correlates with levels of nicotine and derivatives in the baby.[24] Nicotine and derivatives cause alterations in neurodevelopment.[25]
Sleeping
Placing an infant to sleep while lying on the stomach or side rather than on their back increases the risk.[5][26] This increased risk is greatest at two to three months of age.[5] Elevated or reduced room temperature also increases the risk,[27] as does excessive bedding, clothing, soft sleep surfaces, and stuffed animals.[28] 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.[5]
Sharing a bed with parents or siblings increases the risk for SIDS.[29] 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.[5] The risk remains, however, even in parents who do not smoke or use drugs.[30] 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 recommended against devices marketed to make bed-sharing "safe", such as in-bed co-sleepers.[31]
Room sharing as opposed to solitary sleeping is known to decrease the risk of SIDS.[32]
Breastfeeding
Breastfeeding is associated with a lower risk of SIDS.[33] It is not clear if co-sleeping among mothers who breastfeed without any other risk factors increases SIDS risk.[34]
Pregnancy and infant factors
SIDS rates decrease with increasing maternal age, with teenage mothers at greatest risk.[21] Delayed or inadequate prenatal care also increases risk.[21] 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.[35][36] Premature birth increases the risk of SIDS death roughly fourfold.[21][35] From 1995 to 1998, the U.S. 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.[35]
Anemia has also been linked to SIDS[37] (note, however, that per item 6 in the list of epidemiologic characteristics below, extent of anemia cannot be evaluated at autopsy because an infant's total hemoglobin can only be measured during life.[38]). 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.
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