Increased blood pressure variability (BPV) is associated with increased cardiovascular risk [1]. Previous studies have explored the effects of various humoral, environmental and neural factors on BPV in the general population. However, the effect of salt supplementation and renin angiotensin system (RAS) activity on BPV in type 2 diabetes (T2DM) is poorly understood.
We aimed to determine the effect of sodium chloride (NaCl) supplementation on 24hour mean arterial BPV (24hBPV, i.e. short-term blood pressure variability) in the setting of angiotensin II receptor blocker (ARB), telmisartan use and the effects of age, sex, plasma renin activity (PRA) and serum aldosterone on 24hBPV.
In a randomised, double-blind, crossover study, patients with T2DM (n=28), treated with telmisartan 40 mg for a total four weeks received NaCl (100 mmol/24 hr) or placebo capsules in the final two weeks of ARB use. Following a six-week washout, the protocol was repeated in reverse
24hBPV was evaluated as a co-efficient of variation (CV(%)= [mean/standard deviation] x100). 24 hour urinary sodium excretion (24hUNa), ambulatory blood pressure and biochemical tests were performed at each phase. Results were analysed using a linear mixed model.
24hBPV was higher with telmisartan vs predicted baseline (p=0.01), with a trend towards reduced 24hBPV with NaCl supplementation (predicted BPV telmisartan and placebo 11.69% vs predicted BPV telmisartan and NaCl 10.56%, p=0.052). 24hBPV was lower in females (females vs males -0.537%, p=0.17) with increasing age (-0.020% per year age, 95% CI -0.31 to - 0.009, p=0.001) and PRA (-0.015% per unit PRA, 95% CI-0.265 to -0.004, p=0.011). SBP and BPV did not correlate.
In patients with T2DM, 24hBPV was higher with telmisartan use, however there was a trend towards reduced 24hBPV with NaCl supplementation. Of the antihypertensive classes, ARBs may not be as effective at lowering 24hBPV as calcium channel blockers or diuretics.