A lack of answers is part of what makes sudden infant death syndrome (SIDS) so frightening. SIDS is the leading cause of death among infants 1 month to 1 year old, and claims the lives of about 2,500 each year in the United States. It remains unpredictable despite years of research.
Even so, the risk of SIDS can be greatly reduced. First and foremost, infants younger than 1 year old should be placed on their backs to sleep — never face-down on their stomachs or on their sides.
As the name implies, SIDS is the sudden and unexplained death of an infant who is younger than 1 year old. It's a frightening prospect because it can strike without warning, usually in seemingly healthy babies. Most SIDS deaths are associated with sleep (hence the common reference to "crib death") and infants who die of SIDS show no signs of suffering.
While most conditions or diseases usually are diagnosed by the presence of specific symptoms, most SIDS diagnoses come only after all other possible causes of death have been ruled out through a review of the infant's medical history, sleeping environment, and autopsy. This review helps distinguish true SIDS deaths from those resulting from accidents, abuse, and previously undiagnosed conditions, such as cardiac or metabolic disorders.
When considering which babies could be most at risk, no single risk factor is likely to be sufficient to cause a SIDS death. Rather, several risk factors combined may contribute to cause an at-risk infant to die of SIDS.
Most deaths due to SIDS occur between 2 and 4 months of age, and incidence increases during cold weather. African-American infants are twice as likely and Native American infants are about three times more likely to die of SIDS than caucasian infants. More boys than girls fall victim to SIDS.
Other potential risk factors include:
Foremost among these risk factors is stomach sleeping. Numerous studies have found a higher incidence of SIDS among babies placed on their stomachs to sleep than among those sleeping on their backs or sides. Some researchers have hypothesized that stomach sleeping puts pressure on a child's jaw, therefore narrowing the airway and hampering breathing.
Another theory is that stomach sleeping can increase an infant's risk of "rebreathing" his or her own exhaled air, particularly if the infant is sleeping on a soft mattress or with bedding, stuffed toys, or a pillow near the face. In that scenario, the soft surface could create a small enclosure around the baby's mouth and trap exhaled air. As the baby breathes exhaled air, the oxygen level in the body drops and carbon dioxide accumulates. Eventually, this lack of oxygen could contribute to SIDS.
Also, infants who succumb to SIDS may have an abnormality in the arcuate nucleus, a part of the brain that may help control breathing and awakening during sleep. If a baby is breathing stale air and not getting enough oxygen, the brain usually triggers the baby to wake up and cry. That movement changes the breathing and heart rate, making up for the lack of oxygen. But a problem with the arcuate nucleus could deprive the baby of this involuntary reaction and put him or her at greater risk for SIDS.
The striking evidence that stomach sleeping might contribute to the incidence of SIDS led the American Academy of Pediatrics (AAP) to recommend in its 1992 Back to Sleep campaign that all healthy infants younger than 1 year of age be put to sleep on their backs (also known as the supine position).
Since the AAP's recommendation, the rate of SIDS has dropped by more than 50%. Still, SIDS remains the leading cause of death in young infants, so it's important to keep reminding parents about the necessity of back sleeping.
Many parents fear that babies put to sleep on their backs could choke on spit-up or vomit. According to the AAP, however, there is no increased risk of choking for healthy infants who sleep on their backs. (For infants with chronic gastroesophageal reflux (GER) or certain upper airway malformations, sleeping on the stomach may be the better option. The AAP urges parents to consult with their child's doctor in these cases to determine the best sleeping position for the baby.)
Placing infants on their sides to sleep is not a good idea, either, as there's a risk that infants will roll over onto their bellies while they sleep.
Some parents also may be concerned about positional plagiocephaly, a condition in which babies develop a flat spot on the back of their heads from spending too much time lying on their backs. Since the Back to Sleep campaign, this condition has become quite common — but it is usually easily treatable by changing your baby's position frequently and allowing for more "tummy time" while he or she is awake.
Of course, once babies can roll over consistently — usually around 4 to 7 months — they may choose not to stay on their backs all night long. At this point, it's fine to let babies pick a sleep position on their own.
In addition to placing healthy infants on their backs to sleep, the AAP suggests these measures to help reduce the risk of SIDS:
For parents and families who have experienced a SIDS death, many groups, including the Sudden Infant Death Syndrome Alliance, can provide grief counseling, support, and referrals.
And growing public awareness of SIDS and precautions to prevent it should leave fewer parents searching for answers in the future.
Reviewed by: Floyd R. Livingston Jr., MD
Date reviewed: April 2014
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