Vitamin D status and hypertension: a review

Integrated Blood Pressure Control

Apr 2015

DOI: 10.2147/IBPC.S49958

Citations:61

Influential Citations:4

Systematic Reviews / Meta-Analyses

Enhanced Details

Methods

Design: scoping systematic literature review and meta-analysis of observational studies (prospective and cross-sectional). Population: healthy adults (>18 years) from general populations worldwide; ten prospective studies (n=58,262) and 19 cross-sectional studies (n=90,535).

Results

Higher vitamin D status (25OHD) is associated with lower hypertension risk in observational studies. Prospective: RR 0.76 (0.63–0.90) for top vs bottom 25OHD; cross-sectional: OR 0.79 (0.73–0.87). Stronger associations in higher-quality studies and among younger females; no increased risk with older age or vitamin D deficiency. Causality not established due to observational design; Mendelian analyses suggest possible causal link (OR 0.92 per 10% increase in genetically instrumented 25OHD) and reduced SBP/DBP, but randomized trials of vitamin D supplementation show no consistent benefit for hypertension. Large RCTs (e.g., VITAL) are needed to determine whether supplementation reduces hypertension risk. Takeaway: observational data imply an inverse association between vitamin D status and hypertension, but supplementation for hypertension prevention remains unproven.

Limitations

Observational design limits causal inference; substantial heterogeneity across studies; residual confounding and bias possible; variability in 25OHD assays (RIA, CLIA, HPLC) and seasonality; many studies cross-sectional (limited temporality); incomplete adjustment for BMI and other confounders; response rates averaged ~65%; potential generalizability issues across populations and ethnicities.

Abstract

Vitamin D is a steroid prohormone synthesized in the skin following ultraviolet exposure and also achieved through supplemental or dietary intake. While there is strong evidence for its role in maintaining bone and muscle health, there has been recent debate regarding the role of vitamin D deficiency in hypertension based on conflicting epidemiological evidence. Thus, we conducted a scoping systematic literature review and meta-analysis of all observational studies published up to early 2014 in order to map trends in the evidence of this association. Mixed-effect meta-analysis was performed to pool risk estimates from ten prospective studies (n=58,262) (pooled risk for incident hypertension, relative risk [RR] =0.76 (0.63–0.90) for top vs bottom category of 25-hydroxyvitamin D [25OHD]) and from 19 cross-sectional studies (n=90,535) (odds ratio [OR] =0.79 (0.73–0.87)). Findings suggest that the better the assessed quality of the respective study design, the stronger the relationship between higher 25OHD levels and hypertension risk (RR =0.67 (0.51–0.88); OR =0.77 (0.72–0.89)). There was significant heterogeneity among the findings for both prospective and cross-sectional studies, but no evidence of publication bias was shown. There was no increased risk of hypertension when the participants were of older age or when they were vitamin D deficient. Younger females showed strong associations between high 25OHD levels and hypertension risk, especially in prospective studies (RR =0.36 (0.18–0.72); OR =0.62 (0.44–0.87)). Despite the accumulating evidence of a consistent link between vitamin D and blood pressure, these data are observational, so questions still remain in relation to the causality of this relationship. Further studies either combining existing raw data from available cohort studies or conducting further Mendelian analyses are needed to determine whether this represents a causal association. Large randomized controlled trials are also needed to determine whether vitamin supplementation may be beneficial in the prevention or the treatment of hypertension. show less