Overview and Definitions

Each year in the United States, around 3500 infants tragically die of sleep-related infant deaths. This includes infants that die from SIDS, accidental suffocation and strangulation in bed, and a few other causes.

Sudden Unexpected Infant Death (SUID) is used to describe any sudden and unexpected death during infancy. Sometimes, the cause of death can be determined by a specific cause, such as a natural cause, infection or accident.

Sudden Infant Death Syndrome (SIDS) — also called Unexplained Sudden Death in Infancy — describes a sudden unexpected infant death that cannot be explained after a thorough evaluation.

Sleep-Related Deaths includes SUID, SIDS, and and accidental deaths explained by a physical hazard in the sleep environment.

How Often do Infant Sleep-Related Deaths Occur?

In 2020, there were about 1,389 deaths due to SIDS, about 1,062 deaths due to unknown causes, and about 905 deaths due to accidental suffocation and strangulation in bed. Most recent SIDS data still shows that SIDS is rare. There are about 25 infants lost to SIDS for every 100,000 live births. (Data from CDC)

Thankfully, the SIDS Rates have declined 75% since the 1990s, but in 2019, SIDS, was the Second most common cause of infant mortality, followed by accidental suffocation and strangulation in bed (3rd and 4th most common cause of infant mortality)

At what ages do Infant Sleep-Related Deaths Occur?

SUID: ~80% occurs before 0-4 months of age, with a peak at 1-2 months

SIDS: ~90% of cases occur before 6 months of age with a peak at 1-4 months.

Accidental suffocation due to soft bedding: median age 3 months

Accidental suffocation due to overlay: median age 2 months.

Accidental suffocation due to wedging: median age 6 months

(Source: Pediatrics)

Why do Infant Sleep-Related Deaths Occur?

The truthful answer is we don’t know. We know that some infants seem to be more vulnerable to SIDS. SIDS tends to occur at certain stages of neurodevelopment. Also, SIDS is more likely with certain environmental exposures (like overheating or sleeping in any position other than on his/her back).

One leading model is considered the triple risk model, proposed by Filano and Kinney in 1994. This “triple risk model” suggests that SIDS occurs when multiple factors coincide.

In this model, SIDS occurs when a vulnerable infant is exposed to some environmental stressor during a critical stage in development.

What Babies are at Higher Risk for Sleep-Related Deaths?

What causes this intrinsic vulnerability is unclear, but may be related to in-utero environmental conditions, genetics, development or delayed maturation.

In-utero environmental conditions:

• Small for their gestational age (SGA) or growth-restricted infants

• Infants with prenatal cigarette or alcohol exposure

• Twins (have about double the rate of SIDS compared to singleton births)

Genetics:

• Random genetic mutations may increase the risk for SIDS. Genes involved in metabolic function, the immune system, heart, nerves, brain function and development have so far emerged as the most important with respect to SIDS. Note — most of these gene mutations are not known from routine prenatal testing.

• Boys (XY) are at higher risk than girls (XX)

• Siblings of children who died from SIDS are at higher risk

Development:

• Brain (dentate gyrus) and brainstem abnormalities were observed in up to 41% (dentate gyrus) and 70% (brainstem) of infants who die of SIDS

• Preterm infants have 2-3x higher risk than term infants.

There are racial and ethnic differences in the rates of sudden, unexpected infant death and SIDS. Race is a social construct, and can be a proxy for aspects of an individual’s experiences. Adverse childhood experiences are associated with epigenetic changes that may help explain health outcomes.

What Can I Do to Help Prevent Sleep-Related Deaths?

The American Academy of Pediatrics has published 15 recommendations for parents and caregivers that can reduce the risk of SIDS and Sleep-Related Deaths.