Introduction: In the US, blacks are at higher risk of hypertension than whites. The single largest contributor to this disparity is the Southern Diet pattern. Inflammation biomarkers are associated with risk of hypertension, and C-reactive protein (CRP) is higher in blacks than whites. We studied whether elevated CRP in blacks relative to whites contributes to the racial disparity in hypertension in blacks.
Methods: We included 6,548 black and white men and women age ≥45 years from the REGARDS cohort without hypertension at baseline ('03-'07) and who completed visit 2 in '13-'16. Incident hypertension was defined as BP ≥140/90 mm Hg or hypertension medication use at visit 2. Using logistic regression, the black:white odds ratio (OR) for incident hypertension was calculated adjusting for age, sex, race, and baseline SBP. We assessed the percent change in the black:white OR for incident hypertension after adding CRP. The 95% CI was calculated using 1,000 bootstrapped samples. We determined the impact of known hypertension risk factors and anti-inflammatory medications on the percent mediation by CRP.
Results: Hypertension developed in 46% of blacks and 33% of whites. Adjusting for demographics, the black:white OR (95% CI) was 1.51, which was reduced to 1.46, a 9.3% reduction (95% CI 5.4%, 13.2%) by CRP (Table). In models including exercise, waist circumference, BMI, and depressive symptoms, the percent mediation by CRP was 3.7% (1.0%, 6.4%). Similar patterns were seen for models incorporating socioeconomic factors and medication use. After adding Southern diet pattern and dietary Na/K ratio, CRP no longer attenuated the association (1.3% mediation; -1.5, 4.1).
Conclusions: CRP significantly attenuated the black-white difference in incident hypertension; however, once dietary factors were accounted for, CRP had no impact on the black:white difference in incident hypertension. Thus, inflammation as measured by CRP, may be part of the reason that dietary factors influence the black:white disparity in incident hypertension.