Similarities and differences in the epidemiology of pyloric stenosis and SIDS.

Similar temporal declines in infantile hypertrophic pyloric stenosis (IHPS) and sudden infant death syndrome (SIDS) and other common features have led to hypotheses about a shared etiology. We carried out a population-based study to highlight similarities and differences between IHPS and SIDS. We used vital statistics and hospitalization data on all live births in Washington State, USA (1987-2009). Changes in IHPS and SIDS rates over time were quantified using rate ratios with 95 % confidence intervals (CI). The duration between birth and diagnosis of IHPS or SIDS was examined as a function of gestational age at birth. Logistic regression analysis was used to identify risk factors and quantify adjusted temporal trends (2000-2008). Although both IHPS and SIDS rates declined significantly between 1987 and 2008, the patterns and magnitude of the declines (40 and 74 %, respectively) were different. IHPS and SIDS shared risk factors such as maternal smoking and single parent status but other factors showed qualitatively or and quantitatively different associations. Primiparity was a risk factor for IHPS [odds ratio (OR) 1.24, 95 % CI 1.09-1.41], and a protective factor for SIDS (OR 0.44, 95 % CI 0.36-0.55), while male sex had a stronger association with IHPS (OR 4.51, 95 % CI 3.85-5.28 vs 1.36, 95 % CI 1.13-1.64). Both IHPS and SIDS showed significant inverse associations between gestational age at birth and chronologic age at diagnosis/death. IHPS and SIDS share some epidemiologic features and risk factors but other risk factors have qualitatively or quantitatively different effects and recent temporal trends in the two diseases are dissimilar.