Worry about racial discrimination: A missing piece of the puzzle of Black-White disparities in preterm birth?

Objectives The causes of the large and persistent Black-White disparity in preterm birth (PTB) are unknown. It is biologically plausible that chronic stress across a woman's life course could be a contributor. Prior research suggests that chronic worry about experiencing racial discrimination could affect PTB through neuroendocrine, vascular, or immune mechanisms involved in both responses to stress and the initiation of labor. This study aimed to examine the role of chronic worry about racial discrimination in Black-White disparities in PTB. Methods The data source was cross-sectional California statewide-representative surveys of 2,201 Black and 8,122 White, non-Latino, U.S.-born postpartum women with singleton live births during 2011-2014. Chronic worry about racial discrimination (chronic worry) was defined as responses of "very often" or "somewhat often" (vs. "not very often" or "never") to the question: "Overall during your life until now, how often have you worried that you might be treated or viewed unfairly because of your race or ethnic group?" Prevalence ratios (PRs) with 95% Confidence Intervals (CI) were calculated from sequential logistic regression models, before and after adjustment for multiple social/demographic, behavioral, and medical factors, to estimate the magnitude of: (a) PTB risks associated with chronic worry among Black women and among White women; and (b) Black-White disparities in PTB, before and after adjustment for chronic worry. Results Among Black and White women respectively, 36.9 (95% CI 32.9-40.9)% and 5.5 (95% CI 4.5-6.5) % reported chronic worry about racial discrimination; rates were highest among Black women of higher income and education levels. Chronic worry was significantly associated with PTB among Black women before (PR 1.73, 95% CI 1.12-2.67) and after (PR 2.00, 95% CI 1.33-3.01) adjustment for covariates. The unadjusted Black-White disparity in PTB (PR 1.59, 95% CI 1.21-2.09) appeared attenuated and became non-significant after adjustment for chronic worry (PR 1.30, 95% CI 0.93-1.81); it appeared further attenuated after adding the covariates (PR 1.17, 95% CI 0.85-1.63). Conclusions Chronic worry about racial discrimination may play an important role in Black-White disparities in PTB and may help explain the puzzling and repeatedly observed greater PTB disparities among more socioeconomically-advantaged women. Although the single measure of experiences of racial discrimination used in this study precluded examination of the role of other experiences of racial discrimination, such as overt incidents, it is likely that our findings reflect an association between one or more experiences of racial discrimination and PTB. Further research should examine a range of experiences of racial discrimination, including not only chronic worry but other psychological and emotional states and both subtle and overt incidents as well. These dramatic results from a large statewide-representative study add to a growing-but not widely known-literature linking racism-related stress with physical health in general, and shed light on the links between racism-related stress and PTB specifically. Without being causally definitive, this study's findings should stimulate further research and heighten awareness of the potential role of unmeasured social variables, such as diverse experiences of racial discrimination, in racial disparities in health.