The relationship between racial identity, income, stress and C-reactive protein among parous women: implications for preterm birth disparity research.

The persistent racial disparity in preterm birth (PTB)remains one of the most obvious yet poorly understood health disparities in the United States, and current evidence suggests that maternal stress, infection and inflammation may play an important role in the etiology of PTB. In this context, we assessed the complex relationships among racial identity; socioeconomic status (SES); psychosocial factors; and serum C-reactive protein (CRP), an inflammatory biomarker, among parous women in King County, WA. African-American women consistently reported a higher number of stressful life events than white American women (4.6 vs. 2.9, p < 0.001), as well as slightly higher levels of perceived stress and lower social support (24.7 vs. 22.2, p = 0.011, and 3.4 vs. 3.6, p = 0.06, respectively). In the multivariate analysis, African-American race, low-income status and their interaction were all independently associated with CRP; when further adjusted for proximal psychosocial, behavioral and infectious factors, race and income associations were significantly reduced. Stressful life events score was the single best proximal predictor of CRP levels (beta = 0.07 per event,p < 0.001), while perceived stress and social support were not significantly related to CRP. These results support the hypothesis that differences in CRP by racial identity and income may be mediated by differences in proximal risk factors, including stressful life events and health behaviors such as smoking. Objective life event stressors may be important to consider in future studies investigating a potential inflammatory etiology for preterm birth.