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The VitDISH Study: Vit D Supplementation Does Not Improve ISH in Older Patients
Vitamin D supplementation in the VitDISH study did not improve isolated systolic hypertension in elderly patients who were deficient.
Although the role of vitamin D in cardiovascular risk remains controversial, there have been many observational studies that have implicated deficiency in this nutrient with worse cardiovascular outcomes. In addition, many disease states such as stroke and heart failure are associated with lower vitamin D levels. A low level of 25-hydroxy-vitamin D (25-OH-vitamin D), which is the precursor to the active form of vitamin D, is also associated with development of hypertension. Previous meta-analyses of intervention studies have suggested that vitamin D supplementation may reduce blood pressure in select patients.
Given these findings, the high prevalence of isolated “essential” hypertension (isolated systolic hypertension [ISH]) in the elderly, and the need for simple, safe, and inexpensive ways to treat ISH in older patients, Witham and colleagues1 undertook a double-blind placebo controlled randomized trial of vitamin D supplementation in patients >70 years of age with ISH (SBP >140 mmHg; DBP <90 mmHg) and vitamin D deficiency (25-OH-vitamin D <30 ng/mL) in an office-based setting.
The study (VitDISH), published in JAMA Internal Medicine, randomized 159 elderly subjects to either 100 000 U of oral vitamin D or matching placebo every 3 months for a year. Although the 25-OH-vitamin D levels significantly increased at 1 year (+ 8 ng/mL, p<.001) from a mean level of 18 ng/mL, there was no significant treatment effect on office blood pressure, 24-hour blood pressure, markers of vascular health (arterial stiffness, endothelial function), or other secondary outcomes (cholesterol levels, glucose levels, walking distance).1
The authors offered many possible explanations for this lack of benefit, including the presence of “white coat hypertension” which could have diluted the beneficial effects of vitamin D on BP reduction and the lack of a meaningful effect in this patient population. In an accompanying editorial,2 the co-existence of vitamin D deficiency with calcium deficiency was also noted as a possible contributor to this lack of effect. Finally, this small trial, with an endpoint at 1 year may simply have been underpowered to detect a significant effect of vitamin D supplementation, which may still manifest itself at a later time.
Although the VitDISH study does not close the debate on the beneficial effects of vitamin D in cardiovascular risk, it does provide convincing evidence that a large-scale randomized controlled trial of vitamin D supplementation in patients with ISH who are deficient may not be useful. For now, then, there appears to be no role for vitamin D supplementation in reducing blood pressure in the office-based setting.
References:
1. Witham MD, Price RJG, Struthers AD, et al. Cholecalciferol treatment to reduce blood pressure in older patients with isolated systolic hypertension. The VitDISH randomized controlled trial. JAMA Intern Med 2013; DOI:10.1001/jamainternmed.2013.9043.
2. Giovannucci E. Cholecalciferol treatment in older patients with isolated systolic hypertension online first. JAMA Intern Med 2013; DOI:10.1001/jamainternmed.2013.8019.
