Altitude and Variable Effects on Infant Mortality in the United States

Levine, Robert S., Jason L. Salemi, Maria C. Mejia de Grubb, Sarah K. Wood, Lisa Gittner, Hafiz Khan, Michael A. Langston, Baqar A. Husaini, George Rust, and Charles H. Hennekens. Altitude and variable effects on infant mortality in the United States. High Alt Med Biol. 19:265-271, 2018. Aims: To explore whether altitude has different effects on infant mortality from newborn respiratory distress, nontraumatic intracranial hemorrhage, and necrotizing enterocolitis. Results: Infants born in the US Mountain Census Division (AR, CO, ID, NV, NM, UT, and WY) had lower mortality from newborn respiratory distress (p<0.001, mortality rate ratios [MRR]=0.5 for non-Hispanic blacks and non-Hispanic whites and 0.6 for Hispanic whites) relative to infants born elsewhere in the United States, while Mountain Division non-Hispanic white infants had significantly higher mortality from nontraumatic intracranial hemorrhage (MRR=1.3 [1.1, 1.6] p<0.001). After adjustment for state average birth weight, gestational age, and income inequality, a statistically significant, inverse association remained between state average altitude and non-Hispanic white infant mortality from newborn respiratory distress. County altitude (3058 counties in 9 categories from 0 to 7000 feet) was negatively correlated with newborn respiratory distress (r=-0.91, p<0.001) and necrotizing enterocolitis (r=-0.81, p=0.006) at 0 to 7000 feet and positively correlated with nontraumatic intracranial hemorrhage at 0 to 6000-6999 feet (r=0.78, p=0.02). Conclusions: These data show variable cause-specific effects of altitude on infant mortality. Analytic epidemiologic research is needed to confirm or refute the hypotheses generated by these descriptive data.