Objective: To quantify the decreased incidence of sudden infant death syndrome (SIDS) and investigate risk profile changes associated with changes in infant sleep position.
Design: A population-based case-control study that used birth and death certificates from Washington State. Cases (n = 1515) were all singletons born in Washington between 1985 and 1995 (excluding 1991) who died of SIDS. Control cases (n = 6060) were randomly selected singletons born in the same period who did not die of SIDS. Multivariate logistic regression compared changes in the magnitude of associations between risk factors and SIDS before and after 1991.
Results: The incidence of SIDS in Washington declined from 2.6 (1985) to 1.0 (1998) per 1000 births. Over time, the risk of SIDS increased for low birth weight infants (odds ratio [OR] 2.1 rose to 3.6), and infants born to mothers who were smokers (OR 2.7 rose to 3.7), unmarried (OR 1.4 rose to 2.0), black (OR 1.4 rose to 2.5), or received limited prenatal care (OR 1.5 rose to 2.5).
Conclusion: Five exposures were associated with increased risks of SIDS. These may not require a prone sleep position for their deleterious impact being associated with distinct causal pathways, or possibly indicating subpopulations yet to recognize the importance of the supine sleep position.