Effect of Vitamin D Supplementation on Blood Pressure in Elderly People

Study population Adults aged ≥ 60 years with essential hypertension were recruited through nursing homes and physical activity groups in the state of Colima, México. 45 subjects were assessed for eligibility at our out-patient clinic. We excluded subjects with impaired renal or hepatic function; also subjects who had been treated with vitamin D within the last three months.

None were on hormone replacement therapy, but we included subjects on anti-hypertensive for more than 10 years and the dosages were unchanged during the study. Before randomization, two subjects withdrew the informed consent because of personal reasons, and two subjects were excluded due to the diagnosis of severe hypertension.

Design The design was a double-blind, placebo controlled randomized clinical trial. The participants were randomly assigned using a computer-generated randomization code into two groups: group 1 (calcitriol group)with 22 subjects whom were enrolled for 6 weeks of treatment with a daily dose of 1000 IU of cholecalciferol (administered as 1 capsule of 25 μg each) and group 2 with 23 subjects (control group) whom received a similar placebo tablet for also 6 weeks.

During treatment, nine subjects (20%) left the trial due to personal reasons. All patients provided written informed consent. The study was conducted in accordance with the Declaration of Helsinki II and the guidance on Good Clinical Practice (GCP). Approval was obtained from the bioethics committee of the Faculty of Medicine from the University of Colima (FM014/2012).

Measurement At the screening visit prior to randomization, subjects had a routine clinical examination and data concerning medical history. BP was measured 3 consecutive days at the same time, using a kit integrated aneroid sphygmomanometer with stethoscope (medimetrics 5769) with the patient seated and with at least 5 min rest. The subjects with average BP >140/90 mm Hg were included in the study.

Once enrolled in the study groups, anthropometrics measurements were collected. The measurements performed were weight and height with light clothing and no shoes, and the indicator body mass index (kg/m2) was calculated. For the determination of serum 25(OH)D,two blood samples were collected in the morning after an overnight fast of minimum 8 h on the day of the randomization and at the end of the study.

The patients attended control visits every week for safety measures, adverse event registration and assessment of compliance.Returned pills were counted at each visit, and compliance was calculated as the percentage of used pills compared to the expected number.

Biochemistry Serum 25(OH)D concentration were measured with the use of competitive enzyme-linked immunosorbent assay (ELISA: immunodiagnostic, Bernheim, Germany) after solid-phase extraction (reference range: 17-53 pg/mL). The intra- and interassay CVs for the 2 Vitamin D metabolites were <7,0% and 9,0%, respectively.

Statistical Analysis The data were analyzed with the SPSS version 21. The variables studied were described as frequencies, percentages and as median (interquartile range); inferential statistics were performed with non parametric tests (Mann Whitney and related sample Wilcoxon test), and correlations between variables were analyzed by bivariate correlation analysis by Pearson's correlation. Statistical significance was set at a p value < 0.05.