RELATION OF ELECTROLYTES TO BLOOD-PRESSURE IN MEN - THE YI PEOPLE STUDY

The relations of sodium, potassium, calcium, and magnesium to blood pressure were investigated in four groups of men (119 high-mountain Yi farmers, 114 mountainside Yi farmers, 89 Yi migrants, and 97 Han people) with a wide range of electrolyte intake in Puge County, Sichuan Province, People's Republic of China. Electrolytes were measured in diet, serum, and urine. Sodium excretion was 73.9 mmol/24 hr in high-mountain Yi farmers, 117.9 mmol/24 hr in mountainside Yi farmers, 159.4 mmol/24 hr in Yi migrants, and 186.0 mmol/24 hr in the Han people. In ecological correlation analysis, dietary and urinary sodium were significantly and positively correlated with both systolic and diastolic pressure, whereas serum sodium showed no relation with blood pressure. In diet, serum, and urine, potassium was negatively related to systolic and diastolic pressure, whereas the sodium/potassium ratio showed a positive association. With regard to calcium, only urinary excretion was significantly and positively related to blood pressure. No relation was found between magnesium and blood pressure. Analyses at the individual level confirmed the results for sodium and potassium seen at the ecological level, but in addition, dietary calcium and magnesium were significantly and negatively correlated to both systolic and diastolic pressure, and urinary magnesium was inversely related to diastolic pressure. These relations persisted after controlling for age, body mass index (kg/m2), heart rate, alcohol, and total energy intake in multiple regression analysis performed separately for electrolytes in diet, serum, and urine. In multiple regression analysis, an increase in sodium intake of 100 mmol/day corresponded to an increase of 2.3 mm Hg systolic blood pressure and 1.8 mm Hg diastolic pressure. An increase in potassium intake of 100 mmol/day corresponded to an 8.3 mm Hg decrease in systolic blood pressure and a 5.7 mm Hg decrease in diastolic pressure. Using the ratio of urinary sodium, potassium, calcium, and magnesium to creatinine as the independent variables confirmed the previous results, with the addition of a significant inverse relation of magnesium/creatinine ratio to both systolic and diastolic blood pressure. These results are consistent with the view that a diet low in sodium and high in potassium, calcium, and magnesium may prevent the development of hypertension.