Blood pressure is linked to salt intake and modulated by the angiotensinogen gene in normotensive and hypertensive elderly subjects.

OBJECTIVES

To evaluate salt sensitivity in elderly subjects with different forms of hypertension and controls and to investigate any modulation by genotype

DESIGN

Randomized, double-blinded, placebo-controlled latin-square

SETTING

Tertiary referral hospital

PARTICIPANTS

Community subjects (n = 46) aged > or = 60 years classified as isolated systolic hypertension [ISH; systolic blood pressure (SBP) > or = 160, diastolic blood pressure (DBP) < 90 mmHg, n = 19], diastolic +/- systolic hypertension (SDH; DBP > or = 90 mmHg, n = 10) and normotension (SBP < 160, DBP < 90 mmHg, n = 17).

INTERVENTION

Four 14 day treatments, 50, 100, 200 and 300 mmol/day of sodium chloride supplementation interspersed with 14 day washout periods on a salt-restricted diet.

MAIN OUTCOME MEASURES

The 24 h blood pressure, heart rate, weight, urinary sodium and creatinine clearance measured during baseline, treatment and washout periods and angiotensinogen (AGT) and angiotensin converting enzyme (ACE) genotypes.

RESULTS

For the entire cohort, the mean +/- standard error (SE) of change from baseline in SBP for 50, 100, 200 and 300 mmol/day salt was 7.7+/-2.4, 12.1+/-2.4, 16.6+/-3.0, 18.5+/-2.6 mmHg, respectively. For DBP, the respective changes were: -0.1+/-1.5, 2.4+/-1.6, 3.0+/-1.5, 5.8+/-1.7 mmHg. The increase in SBP among ISH subjects was significantly higher than among subjects in the SDH and normotensive groups (P < 0.05). AGT genotype influenced the effect of salt dose on the change in DBP (P = 0.006) but not SBP (P = 0.7).

CONCLUSIONS

In healthy, older subjects, a linear increase in BP occurred with increasing salt dose, it appeared most pronounced in ISH subjects and could be modulated by AGT genotype.