Abstract P246: Relationship Between Urinary Sodium/potassium Ratio And Systolic Blood Pressure In Salt Sensitive Subjects In The Dash-sodium Trial

Abstract

Excessive salt intake is associated with hypertension and cardiovascular morbidity. However, identifying those at risk of salt sensitive hypertension (SSH) remains a challenge due to its unequal distribution among populations and inaccurate assessment of dietary sodium (Na) and potassium (K) intake. The objective of this study was to compare indices of dietary Na intake in relation to systolic blood pressure (SBP) in salt sensitive (SS) and salt resistant (SR) subjects from the Dietary Approaches to Stop Hypertension (DASH)-Sodium trial. We hypothesized that when compared to urinary Na or K independently, Na/K ratio is a better predictor of SSH when defined as a 5-10 mmHg change in SBP from low to high dietary Na. Among 404 Black and White subjects, baseline classifications included 177 SS and 227 SR. After diet randomization, on the control 107 were SS and 92 SR and on the DASH 70 were SS and 135 SR. Descriptive statistics, bivariate analysis, followed by linear regression models for baseline and multilevel mixed-effects models after intervention were used to assess the relationship between SBP and dietary Na (as measured by urinary Na/K ratio or Na and K independently) using SS as a categorical factor. SBP was consistently associated with SS, Na/K ratio, and age in all models . At baseline, SBP was significantly higher in SS and SR subjects of the same race and sex, after controlling for age and urinary Na/K ratio and was highest for White females, SS:142.3 (138.8, 145.7) vs. SR:133.2 (130.7, 135.7), and for Black males, SS:137.0 (133.8, 140.1) vs. SR: 129.6 (127.0, 132.3). On average, SBP increased 1.02 (0.065, 1.98) mmHg with each unit increase in Na/K ratio and 3.30 (2.41, 4.19) mmHg with each 10-year increase in age. After randomization and exposure to increasing levels of sodium, SBP increased in SS subjects on the control diet:125.3 (123.2, 127.3) to 136.8 (134.8, 138.9), an effect that was greater in White vs Black females and in Black vs White males. SBP increased in SS subjects on the DASH diet: 121.4 (118.8, 124.0) to 131.2 (128.7, 133.7), but there were no differences by race and sex. These results suggest that a 5-10 mmHg change in SBP in subjects on a typical American diet and Na/K ratio are good predictors of SSH and that the DASH diet may help to reduce race and sex disparities.