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Causes
By Mayo Clinic staffThe prevalence of SIDS has decreased, due in part to educational campaigns about the importance of placing infants to sleep on their backs. However, SIDS remains the leading cause of death for infants in the first year of life in developed countries.
Over the years, researchers have ruled out a number of possible causes of sudden infant death syndrome, including suffocation, vomiting or choking, birth defects and infection.
Exactly why SIDS occurs remains elusive, but many experts believe multiple factors are involved. For example, it's likely that an infant must have some sort of biological vulnerability, such as a heart or brain defect, combined with an environmental stressor, such as stomach sleeping, and be in a critical developmental period before SIDS can occur. The mother's health and behavior during pregnancy also play a role.
These three factors — vulnerability, critical developmental period and outside stressor — combine within the first six months of an infant's life to form what's known as the triple-risk model.
Research offers clue
Research has offered clues as to what may and what may not be involved in sudden infant death syndrome:
- Brain and nerve characteristics. Researchers have discovered that abnormalities in a part of the brain that helps control breathing and arousal likely play a role in SIDS. Infants who die of SIDS may have brainstems that mature more slowly than those of other infants. Myelin, a fatty substance involved in nerve signal transmission, also may develop more slowly in infants with SIDS.
- Breathing. Other research has focused on the way babies breathe while they're asleep — especially their response to low blood oxygen levels (hypoxia).
- Heart function. Researchers continue to investigate the link between SIDS and long QT syndrome, a subtle electrical disturbance in the heart that causes sudden, extremely rapid heart rates. A study found that almost one in 10 babies who died of SIDS had a genetic defect in one of the genes responsible for long QT syndrome. If there's a history of SIDS in your family, your doctor will want to check for the presence of long QT syndrome in your infant. This usually can be done with an electrocardiogram (ECG) and confirmed, if necessary, with genetic studies.
- Immunizations. After reviewing the available evidence, the American Academy of Pediatrics concluded that childhood immunizations don't play a role in sudden infant death syndrome.
- What is SIDS? U.S. Department of Health and Human Services.www.sidscenter.org/documents/SIDRC/WhatIsSIDS.pdf. Accessed April 30, 2009.
- Moon R, et. al. Sudden infant death syndrome. Lancet. 2007:370:1578.
- Vennemann M, et al. Does breastfeeding reduce the risk of sudden infant death syndrome? Pediatrics 2009:123:e406.
- Baruteau A, et al. Role of congenital long-QT syndrome in unexplained sudden infant death: Proposal for an electrocardiographic screening in relatives. European Journal of Pediatrics. In press. Accessed May 6, 2009.
- Sudden infant death syndrome (SIDS). American Lung Association. http://www.lungusa.org/atf/cf/%7B7a8d42c2-fcca-4604-8ade-7f5d5e762256%7D/ALA_LDD08_SIDS_FINAL.PDF. Accessed April 30, 2009.
- Sudden infant death syndrome fact sheet (SIDS). American Lung Association. http://www.lungusa.org/site/apps/nlnet/content3.aspx?c=dvLUK9O0E&b=2060727&content_id={DD8EAC73-1371-4129-9D82-0220D296D5E9}¬oc=1. Accessed May 7, 2009.
- Task force on sudden infant death syndrome. Policy statement: The changing concept of SIDS. Pediatrics. http://pediatrics.aappublications.org/cgi/content/full/116/5/1245. Accessed April 30, 2009.
- Bacon C. Recurrence of sudden infant death syndrome. Pediatrics. 2008:122;869.
- Blair P, et al. Head covering - a major modifiable risk factor for sudden infant death syndrome: A systematic review. Archives of Disease in Childhood. 2008;93:778.
