ClinicalGeneralPopulation-based analysis of sudden death in children: The Oregon Sudden Unexpected Death Study
Introduction
Sudden death in children is a relatively uncommon but devastating problem. There are few prospective population-based studies, and the annual incidence is poorly defined. Existing retrospective death certificate–based studies suggest that the annual incidence of sudden death in U.S. children ranges between 0.8 and 6.2 per 100,000 population.1, 2, 3 A recent 1-year prospective, population-based analysis of all-ages sudden cardiac arrest (SCA) in a large U.S. community reported that determination of SCA based on death certificates was both inaccurate (positive predictive value 19%) and an overestimate.4 A better estimation of the magnitude of pediatric sudden death with simultaneous evaluation of specific etiologies is likely to be an essential prerequisite for the deployment of future strategies for prevention and resuscitation.
Since the overall magnitude is small, determination of the epidemiology of pediatric sudden death is likely to require a distinct, focused, and intensive effort in a large U.S. subpopulation. As part of the ongoing Oregon Sudden Unexpected Death Study (Ore-SUDS), we performed a prospective, 3-year, community-wide, multiple-source evaluation of pediatric sudden death among the 660,486 residents of Multnomah County, Oregon.
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Methods
All aspects of this investigation were approved by the Institutional Review Board of Oregon Health and Science University as well as the other health systems providing health care to county residents.
Definition of SCA
On the basis of World Health Organization criteria, SCA was defined as sudden unexpected collapse within 1 hour of symptom onset (witnessed), or subjects were to have been observed alive and symptom-free within 24 hours of the event (unwitnessed). Of these, subjects with noncardiac terminal illness or an identifiable noncardiac etiology of sudden death or SCA associated with trauma, violent death, overdose, drowning, and suicide were excluded.
Population evaluated
The Ore-SUDS identified all residents of Multnomah County, Oregon (population 660,486) who had SCA between February 1, 2002, and January 31, 2005, from the following multiple sources: the emergency medical response system, the county medical examiner's office, and 16 area hospitals. This analysis focused on pediatric sudden death (ages 0–17 years).
Postmortem examination
For all cases in which an autopsy was conducted, detailed information, including results of cardiac pathologic examination and toxicology screen, was obtained. Detailed criteria for cardiac pathologic diagnosis have been published elsewhere.5
In-house adjudication of SCA cases
By evaluating all available medical records, a comprehensive evaluation was performed for each case of presumed SCA, including analysis of circumstances of death, medical records, and available autopsy data. All collected clinical information was assembled in a relational database. A process of in-house adjudication was employed to determine cases meeting criteria for SCA. Independent assessments were made by three clinicians, followed by a consensus review. In the event of a disagreement
Pediatric sudden death cases
Pediatric sudden deaths were adjudicated in the same manner as adult cases of SCA. In addition, we assigned a sudden infant death syndrome (SIDS) phenotype to infants with a sudden unexplained death before age 1 year. For all such cases, a detailed postmortem examination was performed to confirm that an etiology of sudden death could not be determined. A standard definition of SIDS was employed6—“the sudden death of an infant under 1 year of age, which remains unexplained after a thorough case
Statistical methods
Descriptive statistics were produced for the pediatric sudden death population using means and standard deviations for continuous variables, and frequencies for categorical variables. Annual incidence rates were calculated by summing the total SCA cases in children aged 0–17 in Multnomah County over 3 years, dividing by 3 to produce an average annual incidence, and dividing by the total county population using U.S. Census year 2000 data (n = 660,486 for the rate per 100,000 population) and the
Annual incidence of sudden death in children
During 2002–2005, a total of 33 children met criteria for sudden death. Overall, the median age was 0.37 years, with an age range of 0.03–12.3 years. A slight majority of the group was female (58%), but this difference was not significant (P = .76). The gender and age-based composition of prospectively determined sudden death cases is shown in Table 1.
The pediatric annual incidence rate per 100,000 population was 1.7 (95% CI 1.1–2.3), compared with 60/100,000 for all ages (Table 1). The
Detailed description and etiology of pediatric sudden death
The majority of sudden deaths (n = 25; 76%) occurred in children age <1 year. Autopsies had been performed on all infants, and physician records were available for 88%. A total of 23 cases (92% of all infants) met the criteria for SIDS. The gender distribution of SIDS cases was similar to that in all pediatric cases, with a nonsignificant trend toward predominance of females (57%, P = .53). For these SIDS cases, the annual incidence rate was 0.8 per 1000 live births. For 22 of the SIDS cases,
Location of events
Half of the infants who met our criteria for SIDS were sleeping in a shared bed or couch at the time of their sudden death (Table 2). Forty-one percent were sleeping in a crib, one infant (5%) was sleeping in a bouncy chair, and one infant was sleeping in an unspecified location. One of the two infants with a congenital defect was asleep; the other was awake.
Among the 22 SIDS cases with information available, about one-quarter (27%) were found in the supine position, while 41% were found in the
Details of attempted resuscitation
Resuscitation was attempted in 64% of pediatric cases. Information regarding the presenting rhythm was available for 22 (67%) of the 33 children. The majority of these children were found to be in asystole (20 of 22; 91%). Two children (9%) presented with VF. One of these two children had return of spontaneous circulation, as did another child found in asystole, but none of the children survived to be discharged from the hospital. In comparison, for adults the return of spontaneous circulation
Summary of main findings
Our study found that pediatric sudden death was a small subgroup (2.8%) of all SCAs in the population during a 3-year time frame, with an annual incidence of 1.7/100,000 population. Previous studies have noted an annual incidence of pediatric sudden death varying from 0.8 to 6.2/100,000.1, 2, 3 Our results indicate that the true incidence is closer to the lower estimate and are in agreement with the study by Driscoll and Edwards,1 who reported an annual incidence of 1.3/100,000 from Olmsted
Conclusions
In this population-based study, the overall incidence of pediatric sudden death was low (3% of total), but SIDS constituted the majority of sudden deaths in children (70% overall, 0.8/1000 live births). Population education to prevent SIDS and emphasis on the role of enhanced postnatal evaluation to diagnose occult heart disease are the two interventions that may have the greatest impact on prevention of sudden death in children.
Acknowledgments
The authors would like to acknowledge the significant contribution of American Medical Response, Portland/Gresham fire departments, the Multnomah County Medical Examiner's office, and the emergency medicine, cardiology, and primary care physicians and allied health personnel of the 16 area hospitals.
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Funded in part by National Heart, Lung and Blood Institute grant no. R01HL088416 (to SSC). SSC is the Pauline and Harold Price Professor at Cedars-Sinai Medical Center, Los Angeles, California.