High sodium in drinking water and its effect on blood pressure.

A recent study of two communities in Massachusetts showed that a group of high school sophomores exposed to 107 mg/liter sodium in their municipal drinking water had significantly higher systolic and diastolic blood pressures than a control group exposed to 8 mg/liter. The present study was undertaken to determine if these results could be repeated in two communities, LaGrange and Westchester, located in the Chicago metropolitan area. These communities have similar demographic and socioeconomic characteristics. However, the concentration of sodium in the municipal drinking water of LaGrange is 405 mg/liter as compared to 4 mg/liter for Westchester. A comparison was made between the blood pressures of high school juniors and seniors from the two communities. Of the 386 eligible students in LaGrange, 84% volunteered to have their blood pressures taken. In Westchester, 78% of the 401 eligible students volunteered. Results of the survey indicated that male and female systolic blood pressures in the high sodium community were not significantly higher than those in the low sodium community. Surprisingly, the observed systolic blood pressures of males in the lower sodium community were higher than those in the high sodium community. These findings did not corroborate the results of the Massachusetts study. However, the male and female diastolic blood pressures were significantly higher (p = 0.040 for males and p = 0.016 for females) in the high sodium community. The increases in diastolic blood pressures (approximately 2 mmHg for males and females) were not as large as those observed in the Massachusetts study (2.7 and 5.1 mmHg for males and females, respectively).