Dynamic changes in place-based measures of structural racism and preterm birth in the USA.

Background: Structurally racist systems, ideologies and processes generate and reinforce inequities among minoritised racial/ethnic groups. Prior cross-sectional literature finds that place-based structural racism, such as the Index of Concentration at the Extremes (ICE), correlates with higher infant morbidity and mortality. We move beyond cross-sectional approaches and examine whether a decline in place-based structural racism over time coincides with a reduced risk of preterm birth across the USA.

Methods: We used as the outcome count of preterm births overall and among non-Hispanic (NH) black and NH white populations across three epochs (1998-2002, 2006-2010, 2014-2018) in 1160 US counties. For our measure of structural racism, we used ICE race/income county measures from the US Census Bureau. County-level fixed effects Poisson models include a population offset (number of live births) and adjust for epoch indicators, per cent poverty and mean maternal age within counties.

Results: An SD increase in ICE (0.11) over time corresponds with a 0.6% reduced risk of preterm birth overall (incidence rate ratio (IRR): 0.994, 95% CI 0.990, 0.998), a 0.6% decrease in preterm risk among NH black births (IRR: 0.994, 95% CI 0.989, 0.999) and a 0.4% decrease among NH white births (IRR: 0.996, 95% CI 0.992, 0.999).

Conclusions: Movement away from county-level concentrated NH black poverty preceded reductions in preterm risk, especially among NH black populations. Our longitudinal design strengthens inference that place-based reductions in structural racism may improve perinatal health. These improvements, however, do not appear sufficient to redress large disparities.