Increased blood pressure in schoolchildren related to high sodium levels in drinking water.

Abstract

SUMMARY The relationship between sodium in drinking water and blood pressure was examined in 348 schoolchildren aged 7-7 to 11-7 years. They were born and living in three areas with different levels of sodium in the public drinking water. Sodium content of the water was either long-term low, long-term high, or short-term high. The three communities are closely comparable according to demographic characteristics. The mean values of systolic and diastolic blood pressure were higher in the high sodium areas. After adjustment for dissimilarities in distributions of weight, height, pulse rate, age, family history of hypertension, and time of blood pressure measurement, these differences remained constant, ranging from 1-8 to 4-0 mm Hg. Girls and boys showed essentially the same differences. Mean 24-hour sodium excretion was somewhat higher in the long-term low area; no differences were found in sodium-creatinine ratio. The regression coefficients between sodium excretion and blood pressure were not significant. The findings from this retrospective follow-up study support the hypothesis that sodium intake influences blood pressure. The association seems to be of a relatively short-term nature, as no differences in blood pressure levels were found between the long-term and short-term high areas.The role of high sodium intake in the pathogenesis of essential hypertension has been emphasised for a long time.' Epidemiologically this is mainly based on comparisons of the mean blood pressure levels of different populations with varying sodium intakes. Within populations, however, the results of blood pressure studies have been equivocal.26 Most of these investigations were cross-sectional, relating a casual blood pressure reading to an estimate of sodium intake at the same time. The major problems of this approach are that the estimates of sodium intake are generally very crude; furthermore, the time-course of the relation between dietary sodium and blood pressure is not taken into account. Therefore, follow-up studies are preferable because these can provide insight into the temporal aspects of the relationship under study.

Water Sodium and Blood Pressure in Rural School Children

“…It is inconsistent with the findings of Tuthill and Calabrese,s Calabrese et al,6 and Hofman et al 7 The first of these studied 606 children who were approximately 15 yr of age in two towns in Massachusetts with water sodium levels of 0.3 and 4.7 mmol/L, respectively; the second study included 608 children approximately 8 yr of age in the same two towns; while the latter studied 348 children from 7 to 11 yr of age in three towns in Holland, one with a low water sodium level (exact level not stated) and two with high water sodium levels (7 mmoI/L). The differences in mean blood pressures between towns in these three studies were statistically significant and implied changes in mean blood pressure of between 0.5 and 1 mm of mercury per 1 mmol/L increase in water sodium level.…”

“…There is no obvious explanation for the disagreement between th is study and those of T uth i II and Calabrese,s Calabrese et al,6 and Hofman et al 7 all of whom used basically similar methods. The number of children in our study and their distribution over three different levels of water sodium would have been sufficient to detect associations, had they been present, of the degree reported by the other investigators.…”

“…This is a well-recognized problem in studies involving comparison of a small number of groups of individuals; for example, our study revealed the possible substantial effect that a simple difference in ambient temperature might have on the results-particularly in a two-group comparison. In the studies of Tuthill and Calabrese 5 and Hofman et al 7 all measurements were taken during a 2-wk period in either spring or autumn, but there was no specific mention of temperature. That Calabrese et aL6 were able to replicate their results in younger children at a different time suggests that the operation of a chance factor, such as ambient temperature, is unlikely.…”

Drinking Water Sodium and Elevated Blood Pressure of Healthy Pregnant Women in Salinity-Affected Coastal Areas

“…13,[22][23][24][25][26] Although some studies failed to show this , sodium concentrations evaluated in this study by far exceeded the sodium levels evaluated in those studies. This is of particular interest because blood pressure is directly related to adverse pregnancy outcomes and may increase the chance of lowfor-gestational-age births.…”

Opinion of the Scientific Panel on Dietetic products, nutrition and allergies [NDA] related to the Tolerable Upper Intake Level of Sodium

“…Even following reversion to a lower sodium intake, this group of infants had higher blood pressure than the breast fed infants at 24 weeks of age. Hofman et al (1980) carried out an observational study of the relationship between blood pressure and the sodium content of drinking water in 348 children aged 7.7 to 11.7 years of age in The Netherlands and demonstrated a relationship between sodium consumption and blood pressure in the short term. They went on to recruit 476 healthy newborns in a single centre during 1980 who were randomized to receive either a low (4.9 mmol/day) or a high sodium diet (13.9 mmol/day), with measurements of blood pressure being taken every 4 weeks.…”