摘要：Objectives. We sought to describe the characteristics and sleep circumstances of infants who die suddenly and unexpectedly and to examine similarities and differences in risk factors among infants whose deaths are classified as resulting from sudden infant death syndrome (SIDS), suffocation, or undetermined causes. Methods. We used 2005 to 2008 data from 9 US states to assess 3136 sleep-related sudden unexpected infant deaths (SUIDs). Results. Only 25% of infants were sleeping in a crib or on their back when found; 70% were on a surface not intended for infant sleep (e.g., adult bed). Importantly, 64% of infants were sharing a sleep surface, and almost half of these infants were sleeping with an adult. Infants whose deaths were classified as suffocation or undetermined cause were significantly more likely than were infants whose deaths were classified as SIDS to be found on a surface not intended for infant sleep and to be sharing that sleep surface. Conclusions. We identified modifiable sleep environment risk factors in a large proportion of the SUIDs assessed in this study. Our results make an important contribution to the mounting evidence that sleep environment hazards contribute to SUIDs. Each year in the United States, more than 4000 infants without prior known illness or injury die suddenly and unexpectedly. 1 Sudden unexpected infant deaths (SUIDs) may result from a variety of causes, some of which are discovered during autopsies or death investigations (e.g., previously undiagnosed metabolic disorders, homicides). One unifying factor is that, in many cases, the cause of death is not determined. Consequently, more than half of SUIDs are ultimately classified as resulting from sudden infant death syndrome (SIDS). 2 SIDS is defined as the sudden death of an infant that remains unexplained after thorough investigation, including autopsy, death scene investigation, and a review of the infant’s clinical history. 3 Approximately 14% of SUIDs are categorized as accidental suffocation, probably as a result of information obtained during death scene investigations. In the case of nearly 30% of SUIDs, the cause remains undetermined and is listed as such on the death certificate. 2 This may occur when the requirements for a SIDS classification are not met (e.g., no death scene investigation or autopsy is conducted). Although SIDS remains a leading cause of infant mortality, SIDS mortality rates in the United States declined from 120.3 per 100 000 live births in 1992 to 54.6 per 100 000 in 2004 4 ; much of this decline has been attributed to national campaigns introduced in 1992 that promoted supine sleep positions for infants. 5 During this same period, infant mortality rates resulting from suffocation and undetermined causes increased from 3.1 and 19.7 per 100 000 live births to 12.5 and 25.3 per 100 000, respectively. 2 It has been noted that this decrease in SIDS and coinciding increase in mortality resulting from suffocation and undetermined causes, particularly since 1999, are the result of a “diagnostic shift” in classification of SUIDs. 2,6–8 The etiology of this diagnostic shift is not fully known; however, it is thought to be a consequence of an increase in death scene investigations and the role of multidisciplinary child death review (CDR) programs in examining and consistently documenting the circumstances of child deaths, as well as more stringent adherence to the definition of SIDS. 2,6,7,9–11 Recognition of the impact of hazards in the infant sleep environment on SUIDs has been increasing in the past several decades. Most of the etiological research on SUIDs has been conducted on deaths classified as SIDS. A recent review by Mitchell comprehensively summarized risk factors for SIDS, including modifiable risk factors related to the infant sleep environment such as prone sleep position, infants sharing a sleep surface with others, and the presence of blankets or other soft bedding. 12 Death certificate data have been used in conducting several large national studies of infant suffocation or deaths of undetermined causes. 2,13 Although use of death certificates allows calculation of rates, few data on sleep circumstances are available, even when written information from the cause of death section of the death certificate is analyzed. 2,4 In a number of small studies, medical examiner records or CDR data from a single urban area or state have been used in assessing SUIDs. 9,14–17 Although these descriptive studies typically provide more detail on the circumstances of the sleep environment, they often involve small sample sizes that do not allow comparisons of characteristics across the 3 categories of SUIDs: SIDS, suffocation, and undetermined cause. The Web-based National Child Death Review Case Reporting System (NCDR-CRS), developed to facilitate consistent collection and reporting of CDR program data, has been available to states since 2005 through the National Center for Child Death Review (NCCDR). 18 CDR typically involves a review of child deaths conducted by a local (e.g., county) or state-level multidisciplinary team. This reporting system includes important information, such as child and parent characteristics, presence of risk factors, and other pertinent circumstances (e.g., details on sleep circumstances), on all deaths related to the sleep environment. The comprehensive compilation of relevant risk factors available in the NCDR-CRS presents a unique opportunity to examine the circumstances of SUIDs in the United States. We used these population-based multistate CDR program data to describe the characteristics and sleep circumstances of infants who die suddenly and unexpectedly and to assess similarities and differences in SUID risk factors among infants whose deaths are ultimately classified as resulting from SIDS, suffocation, or undetermined causes.
