ABSTRACT
BACKGROUND: This is the first study to utilize the index of concentration at the extremes (ICE) to examine risk factors for spina bifida in Texas. The ICE is a useful measure for providing the degree to which residents in a certain area are concentrated into groups at the extremes of disadvantage and privilege. We introduce two novel ICE measures (language and nativity), and three existing ICE measures (race/ethnicity, income, and education), which we applied specifically to Texas residents. METHODS: We used multivariable mixed-model Poisson regression analyses to estimate spina bifida birth prevalence and prevalence ratios among singleton live births in Texas, 1999-2014, for each of our ICE measures. Maternal census tract at delivery was included in the models as a random effect. Analyses were stratified by maternal race/ethnicity (Hispanics and non-Hispanic whites). Live births served as denominators for each category. RESULTS: Among non-Hispanic white women, those in the most disadvantaged versus the advantaged census tract quintile had adjusted relative risk between 1.6 and 8.5 for having a baby affected by spina bifida. However, Hispanic women in the most disadvantaged versus advantaged census tract quintile for four ICE measures had a 33% to 87% lower risk of having an affected pregnancy. CONCLUSIONS: Findings suggest spina bifida risk is associated with neighborhood disadvantage or advantage, and that relationship seems to vary by race-ethnicity. The varied associations between ICE measures and spina bifida by race/ethnicity highlights the importance of using targeted interventions in the prevention of spina bifida.
