Association of Urinary Sodium/Potassium Ratio with Blood Pressure: Sex and Racial Differences

• Published in: Clinical journal of the American Society of Nephrology Vol. 7; no. 2; pp. 315 - 322
• Main Authors: Hedayati, S Susan, Minhajuddin, Abu T, Ijaz, Adeel, Moe, Orson W, Elsayed, Essam F, Reilly, Robert F, Huang, Chou-Long
• Format: Journal Article
• Language: English
• Published: United States American Society of Nephrology 01.02.2012
• Subjects: Adult; African Americans - statistics & numerical data; Albuminuria - ethnology; Albuminuria - etiology; Albuminuria - physiopathology; Albuminuria - urine; Biomarkers - urine; Blood Pressure; Chi-Square Distribution; Continental Population Groups - statistics & numerical data; Cross-Sectional Studies; Female; Glomerular Filtration Rate; Humans; Hypertension - ethnology; Hypertension - etiology; Hypertension - physiopathology; Hypertension - urine; Kidney - physiopathology; Linear Models; Logistic Models; Male; Middle Aged; Multivariate Analysis; Original; Potassium - urine; Risk Assessment; Risk Factors; Sex Factors; Sodium - urine; Texas - epidemiology; Texas
• ISSN: 1555-9041; 1555-905X
• DOI: 10.2215/CJN.02060311

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