Winkleby Lab In the Prevention Research Center

Cooperative Epidemiological Study of Sudden Infant Death Syndrome (SIDS) Risk Factors

This present study will bridge a serious gap in SIDS research created by the virtual absence of case control studies on SIDS in the U.S. The few studies that have been conducted either dealt exclusively with vital statistics data or were plagued by highly variable methods of study and/or the absence of uniform standardized definitions. These problems have severely hampered progress in identifying factors to describe infants at high risk of SIDS. Therefore, the purpose of this study is to elucidate SIDS risk factors.

The primary study objectives are:

1. To identify, from a broad array of infant, maternal, environmental, and medical care variables, risk factors associated with SIDS;

2. To develop a risk prediction scheme which will identify living infants who are at high risk of succumbing to SIDS.

The basic design for this collaborative work is that of a longitudinal case control study. Complete longitudinal SIDS case ascertainment will take place within the cooperative study area during the entire study period. Two living, matched controls will be contemporaneously selected for each SIDS case. Both controls will be matched on age and the second control will be matched additionally on birthweight and when possible, on race.

Comparable data of past events and experiences will be collected on cases and controls through the administration of a questionnaire and the abstraction of variables from the birth certificate; prenatal, delivery, and postnatal medical records. These sources will provide an array of epidemiologic, demographic, medical, behavioral, and environmental variables on cases and controls for comparison and analysis.

Analysis of the data will include estimation of relative risk (or odds ratios), estimation of associations utilizing traditional biostatistical and epidemiological procedures as well as recently developed techniques of logistic regression analysis.

A necropsy protocol will be followed during the post mortem examination of each SIDS case so that standardized tissue and block sections are procured from which slides will be made in the Pathology Coordinating Laboratory. A necropsy checklist and, when available, a dictated autopsy report and results from toxicological, biochemical, microbiological, and roentgenographical tests will also be obtained from County coroners or medical examiners on every case.

This national cooperative study will take place in six different geographic areas, located in five states. The six Study Centers represent the Pacific Northwest, West, Midwest, and East of the United States, and include rural and urban populations of different income and ethnic compositions. The individual Study Centers are listed below, along with the expected number of SIDS cases and controls:

SIDS cases


King County, Washington



California – 9 counties



Chicago, Illinois



St. Louis, Missouri



New York City, New York



Upstate New York – 20 counties






It is anticipated that the combined effort will yield information on approximately 750 SIDS cases and 1500 controls.


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