Dietary sodium and target organ damage in essential hypertension

In addition to its widely contested influence on arterial pressure, dietary sodium may exert some nonpressure-related effects on left ventricular mass in humans. In the present study, we hypothesized that sodium intake (estimated by two consecutive measurements of 24-h urinary sodium excretion) may amplify the effect of arterial pressure on target organ damage (ie, left ventricular mass and microalbuminuria) in a large group of normotensive subjects and patients with never-treated uncomplicated essential hypertension. Left ventricular mass (M-mode echocardiography) and urinary albumin excretion were assessed in 839 subjects (471 men and 368 women) aged 15 to 70 years, with elevated (60%) or normal arterial pressure. In the entire population, multivariate analysis indicated that the relationship between urinary sodium excretion and left ventricular mass index (beta = 0.02, P < .01) as well as urinary albumin excretion (beta = 0.001, P < .0001) was independent from sex, age, body mass index, and systolic arterial pressure. When subjects were divided into quintiles according to urinary sodium excretion, left ventricular mass index and urinary albumin excretion increased significantly from the lowest to the highest quintile in both genders, despite similar values of systolic arterial pressure. The slope of the regression line linking systolic arterial pressure to left ventricular mass index (in men) and urinary albumin excretion (in the entire population) obtained within each quintile of urinary sodium excretion, progressively and linearly increased from the lowest to the highest quintile. These results suggest that sodium intake may amplify the effect of arterial pressure on both the left ventricle and the kidney, and thus suggest that dietary sodium may be an independent factor of cardiovascular risk.