Health and Disease

Sudden Infant Death Syndrome (SIDS): An Unexplainable Nightmare For New Parents

Sudden Infant Death Syndrome (SIDS) is the leading cause of death for infants who are between 1 to 12 months of age in the United States, yet it is broadly defined with much that remains unknown about its cause. The mysterious and unexpected nature of SIDS has raised alarm and resulted in awareness campaigns such as the US “Safe to Sleep” campaign.

By Michelle Li

Published 7:42 PM EST, Tues April 13, 2021


SIDS is the leading cause of death for infants who are 1 month to 12 months in age in the U.S (Marshall). As the name suggests, SIDS is the sudden and unexplained death of a seemingly healthy infant under the age of 1. This most commonly occurs overnight when the infant is sleeping, therefore it is also known as crib death or cot death. Some time after being put to sleep, the infant is discovered lifeless and limp despite showing no health concerns previously. An investigation is then conducted with no clear causes being identified, leading to a diagnosis of SIDS (Odle).

SIDS is responsible for the deaths of 2,500 to 7,000 infants a year. 80% of these deaths occur in infants younger than 5 months old, and, with 60-70% of cases being male deaths, it disproportionately affects boys more than girls (“Sudden Infant Death Syndrome”). SIDS deaths are more frequent during the winter and early spring. Interestingly, babies whose siblings died of SIDS are at a slightly higher risk of the same syndrome despite the fact that it is not contagious or hereditary (Odle). 


SIDS falls under the even broader category of SUIDS, Sudden Unexpected Infant Death Syndrome. For cases labeled as SUIDS, however, the cause of death can generally be identified. It is usually an environmental factor such as high room temperature, being placed to sleep with a pillow, etc. Whereas with SIDS, the cause of death can not be identified even after thorough investigations, autopsies, examinations of death scenes, and reviews of clinical history. Diagnosis of SIDS is a process of exclusion where other causes of death need to be ruled out (Odle). 

SIDS only officially became known as a cause of death in 1979, but sudden deaths in babies with or without explanation have been reported for hundreds of years. In the 1700s and 1800s, SIDS deaths may have been blamed on mothers for rolling on babies while sleeping with them. In the 1900s, co-sleeping between infants and parents became more rare, and speculative reasoning behind the sudden deaths shifted to the dressing of babies in clothes that were too warm during the night (Marshall). This shows how the speculated causes of SIDS change over time.

Speculation About Causes and Current Understanding of SIDS

Many have speculated about the causes of SIDS, and while a number of possible factors have been pointed out, there is still no clearly defined cause of SIDS to this day. One theory is that a genetic defect in an enzyme causes the brain to be deprived of energy, resulting in a coma (Marshall). Another theory focuses on the connection between abnormalities in breathing patterns/heart rhythm and SIDS (Marshall; Odle). Others speculate that a combination of factors and conditions results in SIDS (Odle).

There are also factors that increase the risk of SIDS, including mothers smoking during pregnancy, using drugs or alcohol, being underweight, having children less than one year apart, having children in teen years, and being obese. Babies who are born prematurely, weigh less than 4 pounds, are not breastfed, or are part of a set of twins/triplets/quadruplets are also at an increased risk of SIDS (Odle).

Additionally, the infant’s sleeping positions seem to play a role in deaths diagnosed as SIDS. Studies have shown that placing a baby on its stomach or side to sleep increases the risk of SIDS, as they would re-breathe their own carbon dioxide and would not be able to turn to get more oxygen (“Sudden Infant Death Syndrome”; Odle). This risk is reduced by putting a baby on its back to sleep in the supine sleeping position. Another study also shows that the use of pacifiers may protect against SIDS, reducing the risk of SIDS by 90% (“Sudden Infant Death Syndrome”).

Awareness Campaigns

New Zealand, Australia, and Norway saw campaigns aimed at raising awareness and reducing the risk factors of SIDS. These campaigns resulted in a decrease of SIDS deaths by as much as 50% (Odle). The U.S. also saw a similar campaign, the “Safe to Sleep” campaign, that focused on encouraging parents to put babies on their back when sleeping, as recommended by the American Academy of Pediatrics. The “Safe to Sleep” campaign also saw significant results, reducing the number of SIDS deaths by 20 to 35% in the 1990s. Results from other countries have also shown that a 5 to 10% in babies sleeping on their stomachs results in SIDS deaths decreasing by 70 to 80% (Odle). Although the direct causes of SIDS are still unknown, it seems that sleeping positions are an important risk factor which can be countered by awareness campaigns. 

Disparities in SIDS Deaths

It is also important to note that there are racial/ethnic disparities in SIDS deaths. African American, Native American, and Alaska Native babies all are at a higher risk of SIDS deaths than caucasian babies. African American babies are twice as likely to die from SIDS, while Native American and Alaska Native babies are three times as likely (Odle). Like the causes of SIDS, these disparities are also unexplained. It may be a result of health disparities and cultural differences that make populations more prone to the risk factors of SIDS. Another explanation that is offered is that the efforts of awareness campaigns in different countries are not reaching certain communities.


Sudden Infant Death Syndrome (SIDS) is a cause for concern for many as the leading cause of death for infants who are 1 month to 12 months in age in the U.S. Its unexplained causes and unequal impact on different communities make it an even greater cause for concern. Thankfully, awareness campaigns fighting to reduce the risk factors of SIDS seem to be effective, and there is hope for measures to prevent SIDS in the future as more developments are made to understand SIDS.

Michelle Li, Youth Medical Journal 2021


Marshall, Liz. “Sudden Infant Death Syndrome (SIDS).” The Gale Encyclopedia of Science: S, edited by Katherine H. Nemeh and Jacqueline L. Longe, 6th ed., vol. 7, Gale, 2021, pp. 4314-16. Gale in Context: Science, Accessed 28 Mar. 2021.

Odle, Teresa, and Rebecca J. Frey. “Sudden Infant Death Syndrome.” The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 6th ed., vol. 8, Gale, 2020, pp. 4954-58. Gale in Context: Science, Accessed 28 Mar. 2021.

“Sudden Infant Death Syndrome.” World of Health, Gale, 2007. Gale in Context: Science, Accessed 28 Mar. 2021.


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