The association between urinary sodium excretion and blood pressure in children.

Abstract

SUMMARY This study explored the association between sodium excretion and blood pressure (BP). A new method was used to minimize the measurement error introduced by the large intrinsic variability of 24-hour sodium excretion. The ratio of intra-to interindividual variation was used to estimate the number of measurements needed to characterize the individual. When seven consecutive 24-hour samples were collected from 73 children, ages 11-14 years, a significant correlation between mean individual sodium excretion and BP was demonstrated. The independent relationship persisted when controlling for height, weight, pulse, age, sex and race (p = 0.045), but was eliminated by simultaneously considering mean creatinine excretion. Although the cross-sectional association described is quantitatively weak, a linear relationship between BP and sodium over the range consumed in this society could be important for prevention.CHRONIC HIGH SODIUM INTAKE has long been thought to play a role in the development of high blood pressure.' Cross-cultural comparisons support the hypothesis of a sodium-blood pressure relationship, and extremes of sodium intake, both high and low, have been shown to alter blood pressure.1-2 The association within a population, however, over the range usually ingested by industrialized societies, has been difficult to demonstrate."1-8 Using a new approach, this study shows a positive cross-sectional association between sodium excretion and blood pressure in children ages 11-14 years.'9' 20 MethodsThe study was an extension of a blood pressure survey among children in the parochial schools of Chicago (Levinson S, Berkson D: manuscript in preparation). Through contact with interested science teachers and school personnel, two schools were chosen for an intensive study of the relation of sodium excretion and blood pressure. The proposed study was presented as part of the curriculum to science classes of the sixth through eighth grades and the children were asked, with parental consent, to volunteer. Previous experience and statistical analysis indicated that the crucial methodologic problem involved minimizing sizable measurement error introduced by a high ratio of intra-to interindividual variation in daily sodium excretion.19 Based on findings in adults, we estimated that seven 24-hour urinary sodium determinations were needed to characterize the individual.19Groups of six to 10 children were carefully instructed on the procedure for collection of 24-hour urine samples. The sample was divided into an overnight portion, defined as any urine voided after going to bed at night and first morning void, and daytime sample, the remainder of the day. Carrying cases and plastic bottles were provided each student on a daily basis. Every effort was made to collect the seven samples on consecutive days. When a child was ill, missed school or accidently discarded urine, an additional 24-hour sample was obtained the following week. Although not necessarily the same day of the week, repeat weekday samples were collected ...

Salt and blood pressure in children and adolescents

“…Our finding that salt intake is significantly related to blood pressure is in agreement with the study by Cooper et al 13 who measured sodium excretion from seven consecutive 24-h urine samples in 73 children aged 11-14 years. They found that an increase of 1 g/day in salt intake was associated with an increase of 1 mm Hg in systolic blood pressure, which is greater than that observed in our analysis.…”

“…Measuring sodium from 24-h urine collections is the most accurate method in assessing dietary salt intake. In a carefully conducted study, where seven consecutive 24-h urines were collected by all participants, Cooper et al, 13 in 1980, demonstrated a significant linear relationship between urinary sodium and systolic blood pressure in 73 children aged 11-14 years, that is, the higher the salt intake, the higher the systolic blood pressure. The relationship remained significant after controlling for confounding factors.…”

Salt intake in 3-year-old Japanese children

“…[1][2][3][4] As in adults, the positive relationship between salt intake and blood pressure has already been reported in children. [14][15][16][17][18][19] A large cross-sectional study in Great Britain that investigated 1658 children and adolescents with a mean age of 11±0.1 years showed a significant association of salt intake with systolic blood pressure (SBP). 14 That study estimated that increasing salt intake by 1 g per day would relate to an SBP increase of 0.4 mm Hg.…”

Salt and blood pressure in children

“…Interestingly, the 1980 clinical study by Cooper on 73 black and white school children in Chicago detected what the authors described as a 'quantitatively weak' (although their findings of a 1 mm Hg per gram of sodium increase was greater than seen here) but significant (P ¼ 0.045) relation of sodium to blood pressure. 10 In Chicago, as opposed to the current study, urine collection replaced dietary recall as the basis of estimating sodium intake. Because the earlier study did not capture energy intake and could not assess its potentially confounding effect.…”

“…Children who exercise vigorously may have large energy (and sodium) intakes, and be taller and leaner than youngsters who have the same body mass index and different life styles. Cooper et al 10 postulated that the strong link of creatinine to blood pressure might reflect muscle mass and perhaps be a marker of body size. This, in turn, might be the most powerful determinant of blood pressure in children-more important than age or sodium.…”