A2238 Stronger associations of urinary sodium-to-potassium ratio with blood pressure: results from a prospective cohort study in China

Objectives: To evaluate the association of systolic blood pressure (SBP) and diastolic blood pressure (DBP) with ratio for urinary sodium versus potassium in a large prospective urban and rural epidemiological study in China (PURE-China). Methods: As the important part of global multi-center PURE study, a prospective cohort study was conducted to recruit 46,285 participants in urban and rural area of 12 provinces in China between 2005 and 2009. A single fasting morning urine specimen was collected to test sodium and potassium excretion, and the Kawasaki formula was used to estimate 24-hour urinary sodium and potassium excretion. SBP and DBP were measured with an automated device. Results: Finally, a total of 41,122 subjects were eligible for the analyses of urinary sodium/potassium and blood pressure. Means of estimated urinary sodium and potassium excretion were 5.8 ± 1.8 and 2.1 ± 0.5 gram/day, respectively, and ratio for urinary sodium versus potassium was 2.8 ± 0.8. Adjusted logistic regression analyses showed 1.54 mmHg SBP and 0.44 mmHg DBP increase per 1-g increment of estimated urinary sodium excretion, while 1.18 mmHg SBP and 0.77 mmHg DBP decrease for each gram increase of potassium after adjusted for covariates. Larger increase of SBP and DBP with one unit increase of ratio for sodium versus potassium were observed (4.15 mmHg for SBP and 1.42 mmHg for DBP, P < 0.01). Conclusion: Compared to urinary sodium and potassium, the increase of ratio for sodium vs. potassium is better predictor to detect the SBP and DBP increase. Hence, this ratio should be calculated as an important index when susceptible people are screened for hypertension prevention and control.