Modest Salt Reduction Lowers Blood Pressure in Isolated Systolic Hypertension and Combined Hypertension

Abstract

Many randomized trials have shown that a reduction in salt intake lowers blood pressure in hypertensive individuals. However, few have looked at the effects according to hypertension category. A recent analysis of the third and fourth National Health and Nutrition Examination Survey suggests that salt intake may not be related to blood pressure in isolated systolic or combined hypertension. To look at this further, we reanalyzed the data of our previous salt reduction trials. Hypertensive individuals were studied in randomized double-blind crossover studies: 1 month of usual salt intake compared with 1 month of reduced salt intake. In isolated systolic hypertension (n=24), blood pressure was reduced from 166±19/86±7 to 156±20/85±7 mm Hg (systolic P <0.001; diastolic P =0.459) with a reduction in urinary sodium from 175±51 to 87±38 mmol per 24-hour period (10.3 to 5.1 g per day of salt). In combined hypertension (n=88), blood pressure was reduced from 161±16/100±9 to 154±17/96±9 mm Hg ( P <0.001) with a reduction urinary sodium from 176±65 to 98±51 mmol per 24-hour period (10.4 to 5.8 g per day of salt). These results demonstrate that salt reduction has a significant effect on blood pressure in isolated systolic and combined hypertension. The fall in systolic observed in isolated systolic hypertension would be predicted to reduce stroke by approximately one third, ischemic heart disease by one quarter, and heart failure by one quarter in the population between 60 and 80 years of age, in whom isolated systolic hypertension is the predominate form of hypertension and carries the highest risk. These results provide strong support for universal salt reduction in all hypertensives.