Association of urinary sodium/potassium ratio with blood pressure: sex and racial differences.

Background And Objectives: Previous studies reporting an association between high BP and high sodium and low potassium intake or urinary sodium/potassium ratio (U[Na(+)]/[K(+)]) primarily included white men and did not control for cardiovascular risk factors.

Design, Setting, Participants, & Measurements: This cross-sectional study investigated the association of U[Na(+)]/[K(+)] with BP in 3303 participants using robust linear regression.

Results: Mean age was 43±10 years, 56% of participants were women, and 52% were African American. BP was higher in African Americans than in non-African Americans, 131/81±20/11 versus 120/76±16/9 mmHg (P<0.001). Mean U[Na(+)]/[K(+)] was 4.4±3.0 in African Americans and 4.1±2.5 in non-African Americans (P=0.002), with medians (interquartile ranges) of 3.7 (3.2) and 3.6 (2.8). Systolic BP increased by 1.6 mmHg (95% confidence interval, 1.0, 2.2) and diastolic BP by 1.0 mmHg (95% confidence interval, 0.6, 1.4) for each 3-unit increase in U[Na(+)]/[K(+)] (P<0.001 for both). This association remained significant after adjusting for diabetes mellitus, smoking, body mass index, total cholesterol, GFR, and urine albumin/creatinine ratio. There was no interaction between African-American race and U[Na(+)]/[K(+)], but for any given value of U[Na(+)]/[K(+)], both systolic BP and diastolic BP were higher in African Americans than in non-African Americans. The diastolic BP increase was higher in men than in women per 3-unit increase in U[Na(+)]/[K(+)] (1.6 versus 0.9 mmHg, interaction P=0.03).

Conclusions: Dietary Na(+) excess and K(+) deficiency may play an important role in the pathogenesis of hypertension independent of cardiovascular risk factors. This association may be more pronounced in men than in women.