Vitamin D and risk of future hypertension: meta-analysis of 283,537 participants

The evidence on the association between baseline vitamin D status and risk of incident hypertension in general populations is limited and has not been reliably quantified. We conducted a systematic review and meta-analysis of published prospective studies evaluating the associations of baseline vitamin D status (circulating 25-hydroxyvitamin D [25(OH)D] levels and dietary vitamin D intake) with risk of hypertension. Eligible studies were identified in a literature search of MEDLINE, EMBASE, and Web of Science up to November 2012. Pooled relative risks (RRs) with 95% confidence intervals were calculated using random effects models. Generalized least-squares trend estimation was used to assess dose-response relationships. Of the 2,432 articles reviewed for eligibility, eight unique prospective cohorts with aggregate data on 283,537 non-overlapping participants and 55,816 incident hypertension cases were included. The RRs (95% CIs) for hypertension in a comparison of extreme thirds of baseline levels of vitamin D were 0.70 (0.58, 0.86) for seven studies that measured blood 25(OH) D levels and 1.00 (0.95, 1.05) for four studies that assessed dietary vitamin D intake. The pooled RR of incident hypertension per 10 ng/mL increment in baseline 25(OH)D levels was 0.88 (0.81, 0.97) in dose-response analysis. Evidence was lacking of heterogeneity among studies that measured blood 25(OH) D levels and those that assessed dietary vitamin D status. Studies are needed to determine whether the association of vitamin D with hypertension represents a causal association and also to determine whether vitamin D therapy may be beneficial in the prevention or the treatment of hypertension.