EXTREME CHANGES IN DIETARY-SODIUM EFFECT DAILY VARIABILITY AND LEVEL OF BLOOD-PRESSURE IN BORDERLINE HYPERTENSIVE PATIENTS

This study examined the effect of large changes in dietary sodium on t he average ambulatory blood pressure and its variability in 19 patient s with uncomplicated borderline hypertension. Each patient participate d in a 16-week protocol that consisted of four 4-week periods of diffe rent sodium intake (medium (120-160 mEq/day) during periods 1 and 3 an d low (< 40 mEq/day) or high (> 225 mEq/day) during either period 2 or 4. The 24-hour urine sodium during the low and high periods averaged 18 and 327 mEq/day, respectively, Ambulatory blood pressure monitoring was done at the end of the fourth week of the low and high diet perio ds. During monitoring, pressures were recorded every 15 minutes while awake; in addition, patients kept diaries noting activities, posture, and situation at each measurement. The results show that there was a d ecline of 16/7 mmHg in the average ambulatory awake systolic and diast olic pressures from the high sodium to low sodium diets. Corresponding casual pressures decreased an average of 15 and 8 mmHg, respectively. In examining the factors associated with ambulatory pressure variabil ity, systolic pressure showed greater variation by activity on a low s odium diet than on the high. The findings suggest that sodium restrict ion has a variable, but in some cases marked, effect on lowering the a mbulatory blood pressure in borderline mildly hypertensive patients an d that sodium balance may be important to consider when examining ambu latory blood pressure variability (C) 1994 Wiley-Liss, Inc.