About SIDS

Baby Will

About SIDS

We started babywill.org after losing our baby Will in 2009.  Our mission is to raise awareness and money for research and to help local families impacted by SIDS.  We are not SIDS experts but have tried to become informed so that we can intelligently direct the dollars entrusted to our care, and contribute meaningfully to ongoing efforts to solve SIDS.

Our intent with this page is to make information about SIDS easy to understand.  While we are careful to footnote our sources, some of the things we share represent our best understanding and could be overly simplistic.  We are very open to feedback and corrections if we get something wrong, please just let us know (email: contact-us@babywill.org).  For those who would like further reading, at the bottom of this page we link to our footnotes and additional reading from reputable sources.

Official Definition of SIDS
SIDS is the sudden death of an infant less than 1 year of age that cannot be explained after a thorough investigation is conducted, including a complete autopsy, examination of the death scene, and review of the clinical history.1

It is worth noting that the definition of SIDS has progressed over time.2  We believe this is important not only because it affects the data available about SIDS, but also because it suggests we should expect the definition to continue to evolve as more is learned.  

Diagnosis of Exclusion
Children’s Hospital in Boston explains this concept well:  a baby is determined to have died from SIDS if no cause of death can be identified following a death scene investigation, an autopsy and a review of the clinical history. Thus, SIDS is a known as a “diagnosis of exclusion.”  This means SIDS as a cause of death is determined only when all other causes have been excluded.3

We often hear it said that no one knows why SIDS happens, and suspect this is due to people misinterpreting this notion that SIDS is a diagnosis of exclusion.  As you will read below, quite a bit is known about SIDS and related Sudden Unexpected Infant Death (SUID).

An Underlying Vulnerability in Some Infants
It appears only some babies are susceptible to SIDS.  It is probably about 1 in 1,855 children in the United States.4  According to one of the leading medical theories about SIDS called the Triple Risk Model, these babies have what is referred to as an “underlying vulnerability.”

While researchers cannot yet detect which babies have this underlying vulnerability, evidence shows this vulnerability is likely associated with the development of the baby’s brainstem.5  It is also likely this vulnerability is temporary, occurring only during a critical development period, typically in the first six months of life.6

According to the Triple Risk Model, SIDS does not cause death in normal infants, but only in vulnerable infants with an underlying abnormality.7  We believe this underlying vulnerability is an important factor in trying to understand SIDS because it suggests that when babies are exposed to what would normally be considered harmless things such as lying face down while sleeping or a blanket covering their face, certain babies do not respond normally and can die.

This is very different than children who die from terrible accidents while sleeping such as being pinned between a mattress and a wall or having a co-sleeping adult overlay and accidently suffocate the baby.  However, as you will read below it can sometimes be difficult for investigators to make the distinction between a SIDS death and one attributable to an accident in an unsafe sleep environment.

SIDS is Part of SUID and Why It Matters
SIDS is part of a larger classification of infant deaths referred to as Sudden Unexpected Infant Death (SUID).  This broader classification includes SIDS and other causes of infant death such as Accidental Suffocation, Positional Asphyxia, Overlay, and Undetermined.8

The reason this matters is even when a thorough investigation is conducted, it may be difficult for a medical examiner or coroner to separate SIDS from other types of sudden unexpected infant deaths, especially accidental suffocation in bed.9  This is why all components mentioned in the official definition of SIDS (autopsy, examination of the death scene, and review of clinical history) are necessary to help investigators try and piece together what may have happened when an infant dies unexpectedly during sleep.  

As we understand it, even when the investigation is done properly it can still be difficult to distinguish SIDS from other potential causes.  According to an article published in the New England Journal of Medicine in 2009, the authors state “the diagnosis of asphyxia (suffocation) as the cause of death is subjective, since terminal blood gas levels are obviously unknown. There are no biomarkers that can be obtained posthumously that distinguish between asphyxia-related deaths in normal infants and those in vulnerable infants.”  

We take this to mean that even an expert medical examiner conducting an autopsy might not have any biological evidence to decipher SIDS from some other form of SUID such as an accident.  It also implies that in some cases the distinction between whether a death is ruled SIDS or something else will come from the evidence gathered by police at the death scene rather than hard biological proof obtained in an autopsy.  In fact, there is presently a diagnostic shift underway whereby medical examiners are moving away from using SIDS as a cause of death.  For this reason, you will often here us say “SIDS and related SUID.”  It is also why it is prudent to think of both SIDS and SUID when examining data about SIDS.

Why Emphasize Safe Sleep Environments
Many of the conditions which make a sleep environment unsafe for all babies are the same exogenous factors which pose threats to those babies with an underlying vulnerability that makes them susceptible to SIDS.  So essentially, if we focus on providing a safe sleep environment by removing risky conditions we reduce the risk of both SIDS and these terrible accidents which can happen to even normal children when they are sleeping.

History of SIDS
The term SIDS was only first introduced in 1969, but in all likelihood, children have always been dying from SIDS.  From 1969 until the mid-1980s SIDS was defined somewhat loosely.10  In 1991 the term was more formally defined to resemble its current definition.2

There is an online training manual for SUID which chronicles what is now known as SIDS from the 10th Century until present day.  We found this timeline informative, but also slightly disturbing.  First, it made us grateful for all the work done in a relatively short period of time; federal funds were not earmarked for SIDS until 1973.  But it also pains us to think about how families that lost children years ago had even fewer answers than we do today.  Even more tragic, many SIDS families from just 20, 30, or 40 years ago were even ridiculed for the death of their child, something now known to be completely out of their control.

Back to Sleep Program
During the early 1990s medical studies from Netherlands, Great Britain, Australia, and New Zealand began to suggest a connection between SIDS deaths and babies who were put to sleep on their stomachs.11  In 1992 the American Academy of Pediatrics (AAP) responded by publishing a recommendation that all healthy babies be put to sleep on their backs as a way to reduce the risk of SIDS.12  

In 1994, following the AAP recommendations, the national “Back to Sleep” campaign was launched as a joint effort between the nonprofit First Candle, the AAP, and the National Institute of Child Health and Human Development.13   It was a public relations campaign that encouraged Americans to put babies on their back for sleep.

Without question the Back to Sleep campaign saved lives and was one of the major breakthroughs in attempts to combat SIDS.  Some credit the campaign with reducing the number of SIDS deaths in the US by 50% (see figure 1.1 below).14   

However, in our view, the Back to Sleep campaign was also important because it demonstrated a potent recipe for how to prevent some children from dying.  To be clear, this public relations campaign did not solve SIDS.  It is reasonable to assume that the only way SIDS will be solved is for science to be able to proactively identify which babies have what the Triple Risk Model refers to as an “Underlying Vulnerability.”  But essentially what the Back to Sleep campaign did was advertise one particular risk factor researchers had shown correlated with SIDS (sleeping on the stomach).  This in turn changed behaviors to remove that one external factor from the sleep environment during a critical development period.  Even though this did not solve SIDS, it saved lives while the science continued to advance.

Figure 1.1Graph of SIDS death rates


Why Data About SIDS Can Be Misleading

We have observed that data about SIDS can be misleading for three reasons:  1) Inconsistencies in how SIDS deaths are investigated, 2) the definition of SIDS has changed overtime, and 3) we are in the midst of a diagnostic shift in how SIDS deaths are being classified.  Below we will further explain each in turn.

Inconsistencies in Investigations
In our opinion, the most urgent problem facing SIDS is that there are inconsistencies in how SIDS deaths are investigated.  There are parts of the US where police investigations are more informed and thorough than others.  As we understand it there are also differences in how coroners and medical examiners can classify things they observe during an autopsy.  From what we have read these inconsistencies are due to budgetary constraints, lack of training, ideological differences, and lack of common standards.

As long as there are inconsistencies, it will negatively affect the accuracy of data researchers and others use to try and solve SIDS.  Recent work to standardize and better fund death scene investigations is clearly an important early step in making further progress in the battle against SIDS; not because it will solves SIDS, but because it will improve the data researchers need to solve SIDS.

SIDS Definition has Evolved
The second reason SIDS data can be misleading is that the definition of SIDS has evolved over time.  This is ultimately a good thing because it more precisely aligns the definition with what is known about SIDS.  In the long run, this helps improve the data.  But the downside is historical data can be inaccurate by modern standards.  For instance, the SIDS death rate clearly has come down over the last thirty years, but part of the reason is because some of the deaths previously ruled as SIDS would now by definition be attributed to other things (see figure 1.1).

Diagnostic Shift
The third factor impacting SIDS data is that we are in the midst of what has been called a “diagnostic shift” in how SIDS deaths are being classified.  Essentially, in many parts if the US infant deaths are now being investigated and classified in much more granular detail.  As a result fewer deaths are now being classified as SIDS, and more deaths are being classified as other categories of SUID.15  We view this as a good thing because it makes the data more clear, which in turn helps researchers and public health officials better understand, and hopefully someday even prevent children from dying.

So what happened?  This diagnostic shift can be traced to improving the accuracy and ease of use in the investigation forms used to capture information after an infant dies, as well as an increase in training.  

Prior to 1996 no uniform procedure had been developed for collecting and evaluating information on sudden, unexpected infant deaths (SUIDs) in the United States.  In 1992 Congress recommended that the U.S Department of Health and Human Services Interagency Panel on Sudden Infant Death Syndrome (SIDS) establish a standard scene investigation protocol for SUIDs.16

In 1996 this panel published the first guidelines for death scene investigation of Sudden, Unexplained Infant Death and the first standardized investigation form.  Clearly this was a major step forward.  But in 2001 a national survey indicated that the investigation form was not being used widely because it was poorly organized, lengthy, and cumbersome.17  So in 2004 there was an effort to improve the investigation and reporting of sudden, unexpected infant deaths (SUIDs).

In 2006 the CDC released the Sudden, Unexplained Infant Death Investigation or “SUIDI” Reporting Form for state and local use in infant death-scene investigations.  This SUIDI form replaced the old form that accompanied the 1996 Guidelines for the Death Scene Investigation of Sudden, Unexplained Infant Death.17  The other important thing the CDC did was develop comprehensive training materials for death-scene investigators and a targeted awareness campaign to promote the new form.17

We will provide a link to the current SUIDI form because it is informative for those trying to better understand SIDS.  But please be advised, this is a form used in conjunction with an autopsy.  As a family who lost a child we found parts of the form emotionally upsetting and painful to read.  Here is a link to the current SUIDI form.


Footnotes and Related Links

1 Source:  http://www.cdc.gov/sids/
2 Source:  http://www.childrenshospital.org/az/Site1654/mainpageS1654P1.html
3 Source:  http://www.childrenshospital.org/az/Site1654/mainpageS1654P1.html
4,130,665 births in 2009 – Source:  http://www.cdc.gov/nchs/data/nvsr/nvsr60/nvsr60_01.pdf  (page 2)
2,226 SIDS deaths in 2009 – Source:  http://www.cdc.gov/nchs/data/nvsr/nvsr60/nvsr60_03.pdf (page 12)
Calculation:  4,130,665/2,226 = 1 : 1,855
5 Source:  http://www.childrenshospital.org/az/Site1654/mainpageS1654P1.html
6 Source:  http://pediatrics.aappublications.org/content/116/5/1245.full
7 Source:  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268262/
8 Source:  http://publichealth.columbus.gov/uploadedFiles/Public_Health/Content_Editors/Planning_and_Performance/Child_Fatality_Review/SafeSleepFactSheet_9.25.2012FINAL.pdf
9 Source:  http://www.cdc.gov/sids
10 Source:  http://pediatrics.aappublications.org/content/116/5/1245.full
Corroborating Source:  http://www.nichd.nih.gov/about/overview/timeline/Pages/1970-1979.aspx
11  Source:  http://www.ncbi.nlm.nih.gov/pubmed/1564777
12  Source:  http://www.ncbi.nlm.nih.gov/pubmed/1503575
13  Source:  http://www.firstcandle.org/new-expectant-parents/about-sids-suid/sudden-unexpected-infant-deaths-suid-facts/
14  Source:  http://www.firstcandle.org/new-expectant-parents/about-sids-suid/sudden-unexpected-infant-deaths-suid-facts/
Corroborating Source:  http://www.nichd.nih.gov/SIDS/Pages/sids.aspx
15 Source #1:  http://www.cdc.gov/sids/SUIDAbout.htm
Corroborating Source #2: http://www.sidscenter.org/Statistics.html
Corroborating Source #3:  http://www.ncbi.nlm.nih.gov/pubmed/15867031
Corroborating Source #4:  http://www.ncbi.nlm.nih.gov/pubmed/16582034
Corroborating Source #5:  http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5508a7.htm
Corroborating Source #6:  http://www.ncbi.nlm.nih.gov/pubmed/19171619
16 Source:  http://www.cdc.gov/mmwr/preview/mmwrhtml/00042657.htm
17 Source:  http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5508a7.htm