Video Abstract

Video Abstract

Close modal
BACKGROUND:

Unintentional suffocation is the leading cause of injury death among infants <1 year old in the United States, with 82% being attributable to accidental suffocation and strangulation in bed. Understanding the circumstances surrounding these deaths may inform prevention strategies.

METHODS:

We analyzed data from the population-based Sudden Unexpected Infant Death Case Registry from 2011 to 2014. Cases categorized as explained suffocation with unsafe sleep factors (suffocation), per the Centers for Disease Control and Prevention’s Sudden Unexpected Infant Death Case Registry classification system, were included and assigned a mechanism of obstruction, including soft bedding, overlay, or wedging. We calculated frequencies and percentages of suffocation deaths by mechanism and selected demographic and sleep-environment characteristics.

RESULTS:

Fourteen percent of sudden unexpected infant death cases were classified as suffocation; these cases were most frequently attributed to soft bedding (69%), followed by overlay (19%) and wedging (12%). Median age at death in months varied by mechanism: 3 for soft bedding, 2 for overlay, and 6 for wedging. Soft-bedding deaths occurred most often in an adult bed (49%), in a prone position (82%), and with a blanket (or blankets) obstructing the airway (34%). Overlay deaths occurred most often in an adult bed (71%), and infants were overlaid by the mother (47%). Wedging deaths occurred most often when the infant became entrapped between a mattress and a wall (48%).

CONCLUSIONS:

Safe sleep environments can reduce infant suffocation deaths. Increased knowledge about the characteristics of suffocation deaths can help inform prevention strategies by targeting highest-risk groups.

What’s Known on This Subject:

Unintentional suffocation is the leading cause of injury death among US infants, with 82% attributable to accidental suffocation and strangulation in bed. These deaths are preventable. In Sudden Unexpected Infant Death Case Registry data, airway obstruction is differentiated by mechanism.

What This Study Adds:

Soft-bedding deaths occur more than overlay and wedging deaths. Suffocation by pillows occurs twice as often among infants ≤4 months old. If suffocation deaths had been prevented during the study period, the US sudden unexpected infant death rate would have dropped below the Healthy People 2020 goal.

Unintentional suffocation is the leading cause of injury death among infants (<1 year old) in the United States.1 Eighty-two percent of unintentional infant suffocation deaths are attributed to accidental suffocation and strangulation in bed (ASSB). According to US death-certificate data, rates of infant deaths reported as ASSB per 100 000 live births have increased nearly fourfold, from 6 deaths in 1999 to 23 deaths in 2015.2 This increase is at least partly attributed to changing diagnostic preferences and improved death investigations.2 These injury deaths, often resulting from hazards in the sleep environment, are preventable. Historically, surveillance of infant sleep-related suffocation deaths has relied on underlying cause-of-death codes that are assigned on the basis of the cause of death from death certificates. However, death certificates do not systematically collect information about the circumstances of death. Differentiating a death caused by suffocation from other causes of sudden unexpected infant death (SUID), such as sudden infant death syndrome (SIDS), relies on detailed information from the death-scene investigation and autopsy, for which practices are not standard across jusridictions.3 Furthermore, variations are known to exist in diagnostic preferences and the levels of evidence death certifiers use to designate suffocation as a cause of death, leading to a diagnostic shift in SUID from SIDS to ASSB.2,5 

In 2009, the Centers for Disease Control and Prevention (CDC) created the Sudden Unexpected Infant Death Case Registry to better understand the trends and characteristics associated with SUID, including sleep-related suffocation.6 The SUID Case Registry is built on existing Child Death Review programs and the National Center for Fatality Review and Prevention protocols and data system.7 The Case Registry is a multijurisdictional, population-based surveillance system that monitors SUID cases using data from death-scene investigations, autopsies, medical records, and other relevant data sources. Approximately one-third of US SUID cases are captured in the Case Registry. States participating in the Case Registry receive assistance from the CDC to improve data quality, timeliness, and case ascertainment.

In 2014, the CDC developed the Case Registry classification system to consistently differentiate SUID cases into the following groups: no autopsy or death-scene investigation, incomplete case information, no unsafe sleep factors, unsafe sleep factors, possible suffocation with unsafe sleep factors, and explained suffocations with unsafe sleep factors.8 To understand the factors contributing to and mechanisms of suffocation deaths, the classification system requires the review of detailed information about specific circumstances of each death, including the sleep location and position when found. This information and the resulting classification are important to reliably monitor the incidence of and trends in SUID and SUID subtypes. Identifying factors contributing to suffocation deaths occurring in unsafe sleep environments addresses national and international research priorities9 and may help inform strategies to reduce these deaths. In this study, we describe demographic and sleep-environment characteristics of SUID cases classified as explained suffocation with unsafe sleep factors (suffocation) per the CDC’s SUID Case Registry classification system. This classification requires a high level of evidence of airway obstruction, which is described in detail below.

Using data from the CDC’s SUID Case Registry,6 we analyzed infant deaths that occurred from 2011 through 2014 (the most recent year for which categorized Case Registry data were available) among residents of states participating in the Case Registry. Infants were defined as children <1 year old. We limited the study population to deaths classified as suffocation per the classification system.8 Data were derived from the states participating in the Case Registry at the time of this study, including Arizona, Colorado, Georgia, Louisiana, Michigan, Minnesota, New Hampshire, New Jersey, New Mexico, and Wisconsin. In addition to existing data-use agreements, all states agreed to the use of their deidentified aggregate data for this study.

For these analyses, the authors classified Case Registry cases using the classification system. Cases were classified as suffocation when all of the following criteria were met.8 First, the reported cause on the death certificate was one of the following: unknown; undetermined; SIDS; SUID; unintentional sleep-related asphyxia, suffocation, or strangulation; unspecified suffocation; cardiac or respiratory arrest without other well-defined causes; or ill-defined causes with potentially contributing unsafe sleep factors. Intentional homicides were excluded. Second, a complete death investigation documented where and how the infant was found, and a comprehensive autopsy included (at a minimum) toxicology, imaging, and pathology. Third, the infant was found unresponsive in an unsafe sleep environment with a reliable, nonconflicting witness account of a full external airway obstruction of both the nose and mouth or airway obstruction due to compression of the neck and/or chest. Finally, there were no other potentially fatal findings or concerning conditions (eg, sepsis or congenital birth defect) reported.

Using the classification system, the authors assigned each suffocation case 1 or more mechanisms to which the airway obstruction was attributed. Mechanisms included soft bedding, overlay, wedging, and other.8 Soft bedding was assigned when an infant’s airway was obstructed by an adult mattress, blanket, pillow, couch cushion, or other soft object in the immediate sleep environment. Wedging was assigned when an infant’s airway was obstructed as the result of being trapped or compressed between inanimate objects (eg, a mattress and wall). Overlay was assigned when there was a witnessed account of a person on top of or against an infant, obstructing the infant’s airway. Other was assigned only when the airway obstruction was caused by something in the sleep environment other than soft bedding, overlay, or wedging, such as a plastic bag. Cases could have been assigned >1 mechanism. For example, an infant whose nose and mouth were obstructed by soft bedding (soft bedding), and had his or her neck or chest compressed by a person (overlay).

We derived study variables from individual fields in the National Center for Fatality Review and Prevention’s National Fatality Review Case Reporting System by combining information from different fields or after a qualitative review of written text.10 Selected variables were those most pertinent to the study question with the most complete information recorded. This study includes infants from birth to <1 year old. Age is reported in completed months. For example, 0 months includes infants from birth to <1 month old, and 11 months includes infants from 11 to <12 months old. Medicaid is a state and/or federal health insurance program for people with low income and is used as a proxy for socioeconomic status. Qualitative variables include object obstructing the airway, person sharing the sleep surface with the infant, person who overlaid the infant, body part that overlaid the infant, airway obstruction type, person who overlaid was impaired by drugs or alcohol near the time he or she went to sleep with the infant, and objects infant was wedged between. In cases in which the object that obstructed the airway was an adult mattress, there may have been sheets, blankets, or other bedding materials between the adult mattress and the infant’s airway. We calculated frequencies and percentages of suffocation by mechanism and selected variables, including infant demographics and sleep-environmental factors at the time of death. Per the data-use agreement with states, counts of 1 through 2 are suppressed in an effort to protect confidentiality. Analyses were conducted by using SAS for Windows version 9.3 (SAS Institute, Inc, Cary, NC).

Of 1812 cases in the Case Registry from 2011 through 2014, 250 (14%) were classified as suffocation per the classification system; the remaining cases were classified as unexplained SUID. Of suffocation cases, 219 were assigned 1 mechanism, and 31 were assigned 2 mechanisms. Cases with 2 mechanisms were counted in both mechanism groups; thus, 281 mechanisms were assigned to the 250 cases. Seven cases were assigned the mechanism other. The majority of these infants were suffocated by plastic bags. Because of the small size of this group, these cases are not included in the analyses by mechanism. Of the mechanisms assigned, 190 (69%) were soft bedding, 51 (19%) were overlay, and 33 (12%) were wedging (Table 1).

TABLE 1

Selected Characteristics of Suffocation Deaths Overall (n = 250) and by Mechanism (n = 274): 2011–2014

OverallSoft BeddingOverlayWedging
n%n%n%n%
Overall 250  190 69 51 19 33 12 
Infant sex         
 Male 137 55 104 55 26 51 17 52 
 Female 112 45 85 45 25 49 16 48 
 Missing a a a a a a a a 
Gestational age at birth, wk         
 Preterm, <37 41 16 28 15 13 25 12 
 Term, ≥37 202 81 156 82 37 73 28 85 
 Missing a a a a 
Infant race and/or ethnicity         
 Non-Hispanic white 101 40 75 39 22 43 13 39 
 Non-Hispanic African American 85 34 59 31 22 43 13 39 
 Hispanic 41 16 36 19 a a 
 Other, missing, or unknown 23 20 11 a a 
Infant insured by Medicaid         
 Yes 176 70 130 68 44 86 19 58 
 No 44 18 36 19 21 
 Unknown 30 12 24 13 21 
Location of death         
 Infant’s home 209 84 154 81 45 88 28 85 
 Friend’s or relative’s home 24 10 21 11 
 Day care a a a a 
 Missing or other 10 a a a a 
Exposure to prenatal maternal smoking         
 Yes 89 36 69 36 25 49 27 
 No 138 55 104 55 19 37 21 64 
 Unknown 23 17 14 
OverallSoft BeddingOverlayWedging
n%n%n%n%
Overall 250  190 69 51 19 33 12 
Infant sex         
 Male 137 55 104 55 26 51 17 52 
 Female 112 45 85 45 25 49 16 48 
 Missing a a a a a a a a 
Gestational age at birth, wk         
 Preterm, <37 41 16 28 15 13 25 12 
 Term, ≥37 202 81 156 82 37 73 28 85 
 Missing a a a a 
Infant race and/or ethnicity         
 Non-Hispanic white 101 40 75 39 22 43 13 39 
 Non-Hispanic African American 85 34 59 31 22 43 13 39 
 Hispanic 41 16 36 19 a a 
 Other, missing, or unknown 23 20 11 a a 
Infant insured by Medicaid         
 Yes 176 70 130 68 44 86 19 58 
 No 44 18 36 19 21 
 Unknown 30 12 24 13 21 
Location of death         
 Infant’s home 209 84 154 81 45 88 28 85 
 Friend’s or relative’s home 24 10 21 11 
 Day care a a a a 
 Missing or other 10 a a a a 
Exposure to prenatal maternal smoking         
 Yes 89 36 69 36 25 49 27 
 No 138 55 104 55 19 37 21 64 
 Unknown 23 17 14 

The overall column includes all 250 suffocation cases; cases assigned 2 mechanisms are included in the total for each of the assigned mechanisms.

a

Per the data-use agreement with states, counts of 1 through 2 are suppressed in an effort to protect confidentiality.

A majority of infants were boys, born at term (≥37 weeks’ gestation), non-Hispanic white or African American, and insured by Medicaid (Table 1). The median age at death was 3 months, and most deaths occurred in the infant’s home. The distribution of age at death varied by mechanism (Fig 1). Among soft-bedding deaths, 68% occurred from 1 through 4 months old (median = 3 months old). Among overlay deaths, 71% occurred during the first 2 months of life (median = 2 months), and no deaths occurred after 7 months. More than half (58%) of wedging deaths occurred from 5 through 8 months old (median = 6 months old). Of the 51 suffocation deaths attributed to overlay, 25% were born preterm (<37 weeks’ gestation) compared with 15% among soft bedding and 12% among wedging. Also, 49% of overlay deaths were exposed to prenatal maternal smoking compared with 36% among soft bedding and 27% among wedging.

FIGURE 1

Age distribution for each mechanism of suffocation death (2011–2014; n = 274). In an effort to protect confidentiality and per the data-use agreement with states, percentages in the 1% to 7% range with a numerator of 1 through 2 are all shown on the y-axis at the same level (5%).

FIGURE 1

Age distribution for each mechanism of suffocation death (2011–2014; n = 274). In an effort to protect confidentiality and per the data-use agreement with states, percentages in the 1% to 7% range with a numerator of 1 through 2 are all shown on the y-axis at the same level (5%).

Close modal

Suffocation deaths attributed to soft bedding varied by sleep place, position found, surface-sharing status, and type of object obstructing the airway (Table 2). Among soft-bedding deaths, 49% occurred in an adult bed, and 27% occurred in a crib or bassinet (including portable cribs; Table 2). Most (92%) were found in a nonsupine position. Of the 92 infants (48%) who were found sharing a sleep surface with another person, 61 (66%) were sharing with 1 or both parents, and 24 (26%) were sharing with 1 or more siblings (these groups are not mutually exclusive, nor are data shown in tables). Of the soft objects reported as obstructing the infants’ airways, 34% were blankets, 23% were adult mattresses, and 22% were pillows.

TABLE 2

Suffocation Soft-Bedding Deaths by Age at Death and Sleep Circumstances (n = 190): 2011–2014

All Ages0–4 mo5–11 mo
n%n%n%
Sleep place       
 Adult bed 93 49 71 49 22 50 
 Crib or bassinet 51 27 41 28 10 23 
 Chair or couch 26 14 22 15 
 Other 20 11 12 18 
Position found       
 Prone 155 82 126 86 29 69 
 Side 19 10 10 21 
 Supine 14 10 10 
Sharing a sleep surface with another person       
 No 95 50 69 47 26 59 
 Yes 92 48 75 51 17 39 
 Unknown a a a a 
Object obstructing airway       
 Blanket(s) 64 34 40 27 24 55 
 Adult mattress 44 23 35 24 20 
 Pillow 42 22 37 25 11 
 Couch or recliner cushion 20 11 17 12 
 Multiple objects 10 a a a a 
 Bumper pad a a a a 
 Other 
All Ages0–4 mo5–11 mo
n%n%n%
Sleep place       
 Adult bed 93 49 71 49 22 50 
 Crib or bassinet 51 27 41 28 10 23 
 Chair or couch 26 14 22 15 
 Other 20 11 12 18 
Position found       
 Prone 155 82 126 86 29 69 
 Side 19 10 10 21 
 Supine 14 10 10 
Sharing a sleep surface with another person       
 No 95 50 69 47 26 59 
 Yes 92 48 75 51 17 39 
 Unknown a a a a 
Object obstructing airway       
 Blanket(s) 64 34 40 27 24 55 
 Adult mattress 44 23 35 24 20 
 Pillow 42 22 37 25 11 
 Couch or recliner cushion 20 11 17 12 
 Multiple objects 10 a a a a 
 Bumper pad a a a a 
 Other 

Groups do not equal 100% because of rounding.

a

Per the data-use agreement with states, counts of 1 through 2 are suppressed in an effort to protect confidentiality.

The type of object obstructing the airway differed by infant age. Infants ≤4 months old had their airways obstructed by pillows or couch or recliner cushions approximately twice as often as infants 5 to 11 months old (25% vs 11% for pillows; 12% vs 7% for couch or recliner cushions). Infants 5 to 11 months old had their airways obstructed by blankets approximately twice as often as infants ≤4 months old (55% vs 27%).

Seventy-one percent of overlay deaths occurred in an adult bed, and 51% were found nonsupine (Table 3). Of persons who overlaid these infants, 47% were the mother, 25% were the father, and 22% were a sibling. In 41% of the overlay deaths, the infant was sharing a sleep surface with >1 person. Among overlay deaths, 7 (14%) were overlaid by the mother’s breast (data not shown in tables). Most overlay deaths (71%) were attributed to neck or chest compression as opposed to obstruction of the nose and mouth (22%) or both or unknown (8%). Of the 40 overlay deaths in which an adult overlaid the infant, 23% of the adults were reported to have been impaired by alcohol or drugs around the time they went to sleep with the infant. Among the 10 overlay deaths that occurred after an adult fell asleep while feeding the infant, 7 were breastfeeding (14% of all overlay deaths).

TABLE 3

Suffocation Overlay Deaths by Sleep Circumstances (n = 51): 2011–2014

Age at Death 0–6 moa
n%
Sleep place   
 Adult bed 36 71 
 Chair or couch 13 25 
 Crib or bassinet b b 
 Other b b 
Found position   
 Prone 14 27 
 Side 12 24 
 Supine 25 49 
Person involved with overlay   
 Mother 24 47 
 Father 13 25 
 Sibling 11 22 
 Other 
Airway obstruction mechanism   
 Neck or chest compression 36 71 
 Nose and mouth obstruction 11 22 
 Unknown or both 
Adult fell asleep feeding the infant   
 No or unknown 41 80 
 Yes 10 20 
Feeding type among adults who fell asleep feeding the infant (n = 10)c   
 Breast 70 
 Bottle 30 
Person who overlaid impaired by drugs or alcohol (n = 40)d   
 Yes 23 
 No, not specified, or unknown 31 78 
Age at Death 0–6 moa
n%
Sleep place   
 Adult bed 36 71 
 Chair or couch 13 25 
 Crib or bassinet b b 
 Other b b 
Found position   
 Prone 14 27 
 Side 12 24 
 Supine 25 49 
Person involved with overlay   
 Mother 24 47 
 Father 13 25 
 Sibling 11 22 
 Other 
Airway obstruction mechanism   
 Neck or chest compression 36 71 
 Nose and mouth obstruction 11 22 
 Unknown or both 
Adult fell asleep feeding the infant   
 No or unknown 41 80 
 Yes 10 20 
Feeding type among adults who fell asleep feeding the infant (n = 10)c   
 Breast 70 
 Bottle 30 
Person who overlaid impaired by drugs or alcohol (n = 40)d   
 Yes 23 
 No, not specified, or unknown 31 78 

Groups do not equal 100% because of rounding.

a

There were no deaths after 6 mo of age.

b

Per the data-use agreement with states, counts of 1 through 2 are suppressed in an effort to protect confidentiality.

c

Denominator = adults who fell asleep feeding.

d

Denominator = adult or nonsibling overlays.

Of the 33 suffocation deaths attributed to wedging, 45% were sharing a sleep surface at the time of death, and 73% occurred in an adult bed (Table 4). The objects between which the infant was wedged were most frequently a mattress and wall (48%), followed by a mattress and bed frame (including headboard; 27%). Some infants were wedged between a crib mattress and something else; these cases all involved a crib mattress used with a broken crib or a crib mattress that was ill fitting or not used as recommended (eg, an infant between a crib mattress and an adult mattress that were both placed on the floor or an infant between a crib mattress and the broken rail of a drop-down crib).

TABLE 4

Suffocation Wedging Deaths by Sleep Circumstances (n = 33): 2011–2014

n%
Sleep place   
 Adult bed 24 73 
 Crib or bassinet 12 
 Other (including chair or couch) 15 
Sharing a sleep surface with another person   
 No 17 52 
 Yes 15 45 
 Unknown a a 
Objects infant was wedged between   
 Mattress and wall 16 48 
 Mattress and bed frame 27 
 Crib mattress and other a a 
 Other (eg, in a stroller or between ottoman and couch) a a 
n%
Sleep place   
 Adult bed 24 73 
 Crib or bassinet 12 
 Other (including chair or couch) 15 
Sharing a sleep surface with another person   
 No 17 52 
 Yes 15 45 
 Unknown a a 
Objects infant was wedged between   
 Mattress and wall 16 48 
 Mattress and bed frame 27 
 Crib mattress and other a a 
 Other (eg, in a stroller or between ottoman and couch) a a 
a

Per the data-use agreement with states, counts of 1 through 2 are suppressed in an effort to protect confidentiality.

From 2011 to 2014, 250 of 1812 (14%) Case Registry cases were classified as suffocation as defined by the classification system.8 Suffocation deaths were most frequently attributed to an airway obstruction by soft bedding, followed by overlay and wedging. These deaths represent a small proportion of all SUID cases, but safe sleep environments can prevent suffocation deaths. From 2011 to 2014, the US SUID rate was 87 deaths per 100 000 live births, according to National Center for Health Statistics data.11 If the number of deaths proportionally equivalent to the 14% of Case Registry cases classified as suffocation from 2011 through 2014 had been prevented, the US SUID rate would have dropped to 75 deaths per 100 000 live births, which is below the Healthy People 2020 goal of 84.11,12 

Our study revealed the following commonalities and differences in characteristics of suffocation deaths stratified by mechanism of airway obstruction. Nonsupine sleep position and sleeping in an adult bed were common characteristics among deaths attributed to all 3 mechanisms. Soft-bedding deaths most commonly involved an airway obstruction by blankets. Among overlay deaths, surface sharing with the parent(s) was most common, and infants were most often overlaid by their mothers. Wedging deaths most frequently occurred when the infant became stuck between an adult mattress and a wall.

Our findings reveal that factors and mechanisms of suffocation differ by infant age. Younger infants (≤4 months old) were more often suffocated by overlay or soft bedding than wedging. Younger infants are less likely to get themselves into a wedged position because they are less mobile and cannot roll over on their own. Infants who were suffocated by overlay were youngest and had a higher proportion born preterm than infants who were suffocated by soft bedding or via wedging.

Among soft-bedding deaths, more than half of infants 5 to 11 months old had their airways obstructed by blankets compared with less than one-third of younger infants. Almost half of infants 5 to 11 months old whose airways were obstructed by blankets were entangled in the blankets. It is likely that these older, more developed infants were mobile enough to become entangled in blankets but were not yet coordinated enough to free themselves. Pillows caused the airway obstructions twice as often among infants ≤4 months old compared with infants 5 to 11 months old. Younger infants may have lacked the mobility and neck strength necessary to lift their heads to prevent an airway obstruction, especially when placed prone or on their side on a pillow.13 

The American Academy of Pediatrics (AAP) recommends that infants sleep supine in a safety-approved crib, bassinet, or portable crib with no soft objects or bedding in the sleep area.14 The AAP also recommends that infants share a room but not a sleep surface.14 Following the AAP safe-sleep recommendations can prevent suffocation deaths.

Despite differences in case inclusion criteria, definitions, and the process of assigning cause of death and mechanism, some of our findings are consistent with earlier studies examining infant sleep-related suffocation deaths.15,20 Among suffocation deaths, there was a higher proportion of younger infants.15,17 Overlay deaths were more common among infants 0 to 2 months old, and wedging deaths were more common among infants 3 to 6 months old.17 Pillows, mattresses, and blankets or comforters were the most common objects obstructing infant airways.15 As in our study, most overlay deaths occurred on an adult bed or couch,17,18 and infants were most often overlaid by a parent or sibling.16,18 Although an infrequent occurrence, other studies have also reported overlay deaths when the infant’s mother fell asleep breastfeeding.16 Wedging deaths most commonly occurred between a mattress or bed and wall,15,18 and those that occurred in a crib were related to an ill-fitting mattress or faulty crib.16,17,19 

Our analyses were subject to some limitations. A high level of detailed evidence about the circumstances at death was required to be categorized as suffocation with the classification system. As a result, there may have been infants included in the Case Registry during the study years who were suffocated by hazards in their sleep environments, but the death investigation or documentation lacked the evidence necessary for the case to be categorized as suffocation. Like earlier SUID studies, information about a surface sharer’s drug and alcohol impairment was not documented consistently.21,22 Furthermore, because this was a descriptive study of a population of infants who died, we lacked a comparison group and thus were unable to quantify risk associated with infant sleep practices (ie, there was no control group). Also, the size of the study population limited our ability to make meaningful observations about some of the smaller groups in our stratified analyses.

Despite these limitations, our data source and the resulting analyses have several strengths. Case Registry states committed to conducting population-based SUID surveillance and received targeted assistance and resources from the CDC to improve data quality and completeness.6,7 Earlier studies have used data derived from the National Fatality Review Case Reporting System without restricting cases to those from Case Registry states and thus have had less complete data.23,25 The strengths of Case Registry data address the limitations of other available data sources, such as death certificates. Studies using only death-certificate data lack specifics about the sleep environment and are limited by inconsistent classification of suffocation deaths. Case Registry data include detailed information about the sleep environment, allowing for classification on the basis of strong evidence of suffocation by using standardized criteria and definitions8 and the differentiation of airway obstruction by mechanism. Finally, because complete and comprehensive data about the sleep environment were required to classify a case as suffocation, there were no missing and unknown responses for any sleep-environment variables.

Since 1999, there has been a dramatic increase in the number of US infant deaths attributed to suffocation. These observed rates may not be fully explained by increased incidence and are at least partly attributed to changing diagnostic preferences and improved death investigations.2 Regardless, unintentional injury deaths, such as those categorized as suffocation in our study, can be prevented by following infant safe-sleep practices. The safest place for infants to sleep is on their backs, on an unshared sleep surface, in a crib or bassinet in the caregivers’ room, and without soft bedding (eg, blankets, pillows, and other soft objects) in their sleep area.14 Improving our understanding of the characteristics and risk factors (eg, age differences and sleep-environment characteristics) of suffocation deaths by mechanism of airway obstruction can inform the development of more targeted strategies to prevent these injuries and deaths.

Ms Erck Lambert conceptualized and designed the study, conducted all analyses, drafted the initial manuscript, and reviewed and revised the manuscript; Drs Parks, Hauck, and Shapiro-Mendoza, Ms Cottengim, and Ms Faulkner conceptualized and designed the study and critically reviewed and revised the manuscript; and all authors approved the final manuscript as submitted.

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

FUNDING: Ms Erck Lambert was supported by a contract between DB Consulting Group and the Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention (prime contract number: hhsn316201200076w, task order number: 200-2017-f-94805). Ms Faulkner’s agency, the Michigan Public Health Institute, received funds from the Centers for Disease Control and Prevention in the amount of $789 723.16 for the period August 18, 2013 to June 17, 2018 to support components of the SUID Case Registry described in the article (contract number: 200-2013-56409).

We acknowledge the Sudden Unexpected Infant Death Case Registry teams in Arizona, Colorado, Georgia, Louisiana, Michigan, Minnesota, New Hampshire, New Jersey, New Mexico, and Wisconsin for participating in and supporting this project by allowing access to the data contained in this report.

     
  • AAP

    American Academy of Pediatrics

  •  
  • ASSB

    accidental suffocation and strangulation in bed

  •  
  • CDC

    Centers for Disease Control and Prevention

  •  
  • SIDS

    sudden infant death syndrome

  •  
  • SUID

    sudden unexpected infant death

1
National Center for Health Statistics, National Vital Statistics System
. 10 leading causes of injury deaths by age group highlighting unintentional injury deaths, United States – 2015. 2015. Available at: https://www.cdc.gov/injury/wisqars/pdf/leading_causes_of_injury_deaths_highlighting_unintentional_injury_2015-a.pdf. Accessed January 18, 2018
2
Erck Lambert
AB
,
Parks
SE
,
Shapiro-Mendoza
CK
.
National and state trends in sudden unexpected infant death: 1990-2015.
Pediatrics
.
2018
;
141
(
3
):
e20173519
[PubMed]
3
Erck Lambert
AB
,
Parks
SE
,
Camperlengo
L
, et al
.
Death scene investigation and autopsy practices in sudden unexpected infant deaths.
J Pediatr
.
2016
;
174
:
84
90.e1
[PubMed]
4
Shapiro-Mendoza
CK
,
Parks
SE
,
Brustrom
J
, et al
.
Variations in cause-of-death determination for sudden unexpected infant deaths.
Pediatrics
.
2017
;
140
(
1
):
e20170087
[PubMed]
5
Shapiro-Mendoza
CK
,
Kimball
M
,
Tomashek
KM
,
Anderson
RN
,
Blanding
S
.
US infant mortality trends attributable to accidental suffocation and strangulation in bed from 1984 through 2004: are rates increasing?
Pediatrics
.
2009
;
123
(
2
):
533
539
[PubMed]
6
Shapiro-Mendoza
CK
,
Camperlengo
LT
,
Kim
SY
,
Covington
T
.
The sudden unexpected infant death case registry: a method to improve surveillance.
Pediatrics
.
2012
;
129
(
2
). Available at: www.pediatrics.org/cgi/content/full/129/2/e486
[PubMed]
7
Covington
TM
.
The US National Child Death review case reporting system.
Inj Prev
.
2011
;
17
(
suppl 1
):
i34
i37
[PubMed]
8
Shapiro-Mendoza
CK
,
Camperlengo
L
,
Ludvigsen
R
, et al
.
Classification system for the sudden unexpected infant death case registry and its application.
Pediatrics
.
2014
;
134
(
1
). Available at: www.pediatrics.org/cgi/content/full/134/1/e210
[PubMed]
9
Hauck
FR
,
McEntire
BL
,
Raven
LK
, et al
.
Research priorities in sudden unexpected infant death: an international consensus.
Pediatrics
.
2017
;
140
(
2
):
e20163514
[PubMed]
10
The National Center for the Review and Prevention of Child Death
. Child death review case reporting system data dictionary, version 5. Available at: https://www.ncfrp.org/wp-content/uploads/NCRPCD-Docs/DataDictionary_v5.pdf. Accessed June 16, 2016
11
Centers for Disease Control and Prevention
. About compressed mortality, 1999-2015. 2016. Available at: http://wonder.cdc.gov/cmf-icd10.html. Accessed June 13, 2016
12
US Department of Health and Human Services
. Morbidity and mortality. 2016. Available at: https://www.healthypeople.gov/2020/topics-objectives/objective/mich-19-0. Accessed October 31, 2016
13
American Academy of Pediatrics
.
Bright Futures: Guidelines for Health Supervision of Infants, Children, and Adolescents
.
Elk Grove Village, IL
:
National Center for Education in Maternal and Child Health and Georgetown University
;
2008
14
Task Force on Sudden Infant Death Syndrome
.
SIDS and other sleep-related infant deaths: updated 2016 recommendations for a safe infant sleeping environment.
Pediatrics
.
2016
;
138
(
5
):
e20162938
15
Gaw
CE
,
Chounthirath
T
,
Midgett
J
,
Quinlan
K
,
Smith
GA
.
Types of objects in the sleep environment associated with infant suffocation and strangulation.
Acad Pediatr
.
2017
;
17
(
8
):
893
901
[PubMed]
16
Hayman
RM
,
McDonald
G
,
Baker
NJ
,
Mitchell
EA
,
Dalziel
SR
.
Infant suffocation in place of sleep: New Zealand national data 2002-2009.
Arch Dis Child
.
2015
;
100
(
7
):
610
614
[PubMed]
17
Drago
DA
,
Dannenberg
AL
.
Infant mechanical suffocation deaths in the United States, 1980-1997.
Pediatrics
.
1999
;
103
(
5
). Available at: www.pediatrics.org/cgi/content/full/103/5/e59
[PubMed]
18
Collins
KA
.
Death by overlaying and wedging: a 15-year retrospective study.
Am J Forensic Med Pathol
.
2001
;
22
(
2
):
155
159
[PubMed]
19
Kemp
JS
,
Unger
B
,
Wilkins
D
, et al
.
Unsafe sleep practices and an analysis of bedsharing among infants dying suddenly and unexpectedly: results of a four-year, population-based, death-scene investigation study of sudden infant death syndrome and related deaths.
Pediatrics
.
2000
;
106
(
3
). Available at: www.pediatrics.org/cgi/content/full/106/3/e41
[PubMed]
20
Li
L
,
Fowler
D
,
Liu
L
,
Ripple
MG
,
Lambros
Z
,
Smialek
JE
.
Investigation of sudden infant deaths in the State of Maryland (1990-2000).
Forensic Sci Int
.
2005
;
148
(
2–3
):
85
92
[PubMed]
21
Blair
PS
,
Sidebotham
P
,
Pease
A
,
Fleming
PJ
.
Bed-sharing in the absence of hazardous circumstances: is there a risk of sudden infant death syndrome? An analysis from two case-control studies conducted in the UK.
PLoS One
.
2014
;
9
(
9
):
e107799
[PubMed]
22
Carpenter
R
,
McGarvey
C
,
Mitchell
EA
, et al
.
Bed sharing when parents do not smoke: is there a risk of SIDS? An individual level analysis of five major case-control studies.
BMJ Open
.
2013
;
3
(
5
):
e002299
[PubMed]
23
Schnitzer
PG
,
Covington
TM
,
Dykstra
HK
.
Sudden unexpected infant deaths: sleep environment and circumstances.
Am J Public Health
.
2012
;
102
(
6
):
1204
1212
[PubMed]
24
Lagon
E
,
Moon
RY
,
Colvin
JD
.
Characteristics of infant deaths during sleep while under nonparental supervision.
J Pediatr
.
2018
;
197
:
57
62.e36
[PubMed]
25
Kassa
H
,
Moon
RY
,
Colvin
JD
.
Risk factors for sleep-related infant deaths in in-home and out-of-home settings [published correction appears in Pediatrics. 2018;141(2):e20173633].
Pediatrics
.
2016
;
138
(
5
):
e20161124
[PubMed]

Competing Interests

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: Ms Erck Lambert was supported by a contract between DB Consulting Group and the Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention (prime contract: hhsn316201200076w; task order number: 200-2017-f-94805). Ms Faulkner’s agency, the Michigan Public Health Institute, received funds from the Centers for Disease Control and Prevention in the amount of $789 723.16 for the period of August 18, 2013 to June 17, 2018, to support components of the Sudden Unexpected Infant Death Case Registry described in the article (contract: 200-2013-56409); the other authors have indicated they have no financial relationships relevant to this article to disclose.