Associations of Dietary Sodium Intake and Hyperglycemia on Resting and Stress-Reactive Blood Pressure and Underlying Hemodynamics in Blacks and Whites

Sustained high blood pressure (BP) or hypertension has been identified as the largest single attributable risk factor for cardiovascular and cerebrovascular death. The stark racial disparity in hypertension prevalence between black and white Americans has been documented for nearly a century and is associated with a greater burden from target end-organ damage for blacks. Chronic stress, high-sodium intake and hyperglycemia are key factors that are thought to contribute to racial disparities in hypertension. The purpose of this study was to investigate whether synergistic relations of dietary sodium intake and hyperglycemia are associated with resting and reactive BP and whether these associations differ between black and white adults. The participants were 732 (61% black; 52% below poverty status) Baltimore residents who participated in the Health Aging in Neighborhoods of Diversity Across the Life Span (HANDLS) study. It was hypothesized that hyperglycemia would moderate the influence of dietary sodium intake on resting BP and underlying hemodynamics in blacks but not in whites. Additionally, hyperglycemia was expected to moderate the influence of dietary sodium intake on BP and underlying hemodynamic reactivity to emotion provocation (anger and happy) in blacks but not in whites. Multiple linear regression analyses revealed that hyperglycemia moderated the influence of sodium intake on diastolic BP (DBP), total peripheral resistance (TPR) and cardiac index (CI) in blacks but not in whites. Blacks with hyperglycemia (within the diabetic range) who consumed higher levels of dietary sodium had higher resting DBP and TPR and lower CI compared with blacks with normal glucose levels. Mixed-effects regression models revealed that the interaction of sodium intake, hyperglycemia, and condition/curvilinear condition was not associated with cardiovascular reactivity to emotion provocation, with the exception of SBP and CI in whites during happy recall. It was discovered that the interaction of sodium intake and hyperglycemia was associated with DBP elevations across all conditions of emotion provocation within blacks. Although it was not the main focus of this investigation, it was also discovered that hyperglycemia was associated with differential patterns of CVR in blacks and whites. The results within blacks suggest that the synergistic influence of high-sodium and hyperglycemia results in higher DBP during resting conditions as well as across conditions of emotion provocation. The results within whites suggest that the synergistic influence of high-sodium and hyperglycemia result in greater myocardial reactivity to happy recall. Additionally, the present findings suggest that glycemic status is a potentially important determinant of CVR for both blacks and whites. Further research is needed to confirm whether the results observed during conditions of seated rest and emotion provocation generalize to ambulatory BP and are predictive of future development of hypertension. These findings provide preliminary support that the synergistic relation of high-sodium intake and hyperglycemia may be contributing to the high rates of hypertension in black Americans and provides a promising new direction for health disparities research.