Background: Research has indicated that income inequality (the gap between rich and poor) within a residential area, is associated with infant mortality. One proposed way to decrease income inequality is to increase minimum wage. Ecological studies have identified a relationship between increasing state-level minimum wage and decreased infant mortality rates. We aim to elucidate the relationship between state-level income inequality and individual-level infant mortality risk.

Methods: Data are from US Vital Statistics 2010 Cohort Linked Birth and Infant Death (LBID) records and the 2010 US Bureau of Labor Statistics. We fit multilevel logistic regression models to test whether US state minimum wage was associated with the likelihood of infant mortality (death before the first birthday), while adjusting for individual-level, and state-level confounders. Minimum wage was standardized using the z-transformation and was dichotomized high vs. low using the 75th percentile as a threshold. Analyses were also stratified by mother's race (black vs. white).

Results: The average state-level minimum wage was $7.46, and ranged from $6.15 to $8.15. No significant relationship was observed when minimum wage z-score was tested. High minimum wage (OR=0.93, 95%CI=0.83,1.03) was associated with decreased odds of infant mortality, but was not significant. High minimum wage was significantly associated with reduced infant mortality among black infants (OR=0.80, 95%CI=0.68,0.94), but not among white infants (OR=1.04, 95%CI=0.92,1.17).

Conclusions: Increasing minimum wage might be beneficial to infant health, especially among black infants and can help decrease the racial disparity in infant mortality. Future research should examine whether this association is causal.