Effect of vitamin D supplementation on orthostatic hypotension: data from the vitamin D in isolated systolic hypertension randomized controlled trial.

Orthostatic hypotension commonly accompanies supine hypertension, and is associated with low 25-hydroxyvitamin D levels. We tested whether high-dose intermittent oral vitamin D therapy could ameliorate orthostatic hypotension in older patients with isolated systolic hypertension. We conducted a subgroup analysis of data from a parallel-group, double-blind, randomized, placebo-controlled trial. Patients aged over 70 years with supine office SBP above 140 mmHg and DBP below 90 mmHg received 100 000 units oral vitamin D3 or matching placebo every 3 months for 1 year. Office supine and standing blood pressure were measured at baseline, and 3, 6, 9 and 12 months, along with arterial stiffness and flow-mediated dilatation of the brachial artery. Of 159 patients randomized to the main trial, 75 patients with orthostatic hypotension at baseline were included in this analysis. The mean age was 78 (SD 5) years, baseline blood pressure was 162/76 mmHg and the mean baseline orthostatic fall in blood pressure on standing was 32/5 mmHg. After adjustment for baseline age, 25-hydroxyvitamin D, SBP and orthostatic fall, the fall in SBP was less in the vitamin D group at 3 months [treatment effect 6 mmHg, 95% confidence interval (CI) 0 to 12], but repeated-measures analysis showed no significant treatment effect (3 mmHg for systolic fall, 95% CI -1 to 8; 1 mmHg for diastolic fall, 95% CI -1 to 3). Twelve months of intermittent, high-dose oral vitamin D3 did not significantly improve orthostatic hypotension in older patients with isolated systolic hypertension.