Sodium excretion and blood pressure (original) (raw)

The urinary excretion of sodium, potassium, and water during three 24-hour periods were related to blood pressure in a sample of 49-year-old men. Of 3205 49-year-old men liring in Goteborg, 2376 (74%) took part in the blood pressure screening, and, of these, 120 subjects having blood pressures from the lowest to the highest were selected by systematic sampling based on diastolic blood pressure. Only subjects who were not on antihypertensive treatment were included. Results showed a marked day-today variation in sodium excretion, with between-days r values of 0.23-0.64. The variation was less for two consecutive days than for two nonconsecutive days. The mean urinary excretion and the diurnal rhythm of sodium, potassium, and water did not differ significantly among normotensive, borderline, and hypertensive subjects. Over a wide range of blood pressures, no correlation was found between blood pressure and the urinary excretion of sodium, potassium, or water. In the low blood pressure range, however, there was a significant positive correlation between blood pressure and urinary sodium excretion (R = 0.46,p < 0.01; R = Spearman's coefficient of rank correlation). The large intraindiridual variation in sodium excretion and blood pressure makes it difficult to estimate an individual's mean values. Furthermore, there are limitations in drawing longitudinal conclusions from crosssectional data. With these methodological problems in mind, our findings indicate that salt intake influences blood pressure in a part of the normotensire population, but do not lend support to the hypothesis that habitual salt intake might be of major importance for the blood pressure level in mild to moderate essential hypertension. (Hypertension 3: 318-326, 1981) KEY WORDS • blood pressure • essential hypertension • sodium excretion potassium excretion • body size • epidemiology A positive relationship between salt intake and the prevalence of hypertension in both primitive and more developed societies has been found in a great number of investigations. 1 ' s In societies with extremely low sodium intake (< 10 mmole/24 hr) and high potassium intake, hypertension seems to be absent and blood pressure does not seem to rise with age. In societies with high sodium intake (> 350 mmole/24 hr), 30% or more of From the Sections of Preventive Cardiology and Nephrology,