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 ≥ 60 years classified as isolated systolic hypertension [ISH; systolic blood pressure (SBP) ≥ 160, diastolic blood pressure (DBP) < 90 mmHg, n = 19], diastolic ± systolic hypertension (SDH; DBP ≥ 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.