Introduction: Observational data link low 25-hydroxyvitamin D levels to both prevalent blood pressure and incident hypertension. Although existing trial data suggest a possible antihypertensive effect of vitamin D supplementation, no trial has examined the effect of vitamin D supplementation in isolated systolic hypertension, the commonest pattern of hypertension in older people.
Methods: Parallel group, double blind, placebo controlled, randomised trial. Patients aged 70 and over with isolated systolic hypertension (supine systolic >140 mm Hg, supine diastolic <90 mm Hg) were recruited from clinics and primary care. Participants were randomised to receive either 100,000 units oral vitamin D3 or matching placebo every 3 months for a year. The primary outcome measure measured every 3 months was office blood pressure; secondary outcomes included 24-h blood pressure, arterial stiffness measured using applanation tonometry, endothelial function measured using flow-mediated dilatation of the brachial artery, cholesterol, insulin resistance, B-type natriuretic peptide levels, falls and 6-minute walk distance.
Results: A total of 159 participants were randomised, mean age 77 years. The mean baseline office systolic blood pressure was 163/78 mmHg, and mean baseline 25-hydroxyvitamin D level was 45 nmol/l; 25-hydroxyvitamin D levels rose in the treatment group compared with the placebo group (+20 nmol/l at 1 year, P < 0.001). No significant effect was evident on the primary outcome of change in office blood pressure (−0.7/−1.6 mmHg for vitamin D compared with placebo at 3 months; +1.1/ + 0.3 mmHg overall treatment effect). No effect was evident on any of the secondary outcomes (24-h blood pressure, arterial stiffness, endothelial function, cholesterol, glucose, walk distance). There was no excess of adverse events in the treatment group; total number of falls was non-significantly lower in the vitamin D group (36 versus 46, P = 0.24).
Conclusion: Vitamin D supplementation did not improve blood pressure or markers of vascular health in older patients with isolated systolic hypertension.