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

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.