Objective: To examine the association of serum vitamin D level with metabolic syndrome (MetS) and hypertension (HTN) in middle-aged Korean subjects.
Design and subjects: We conducted a population-based, cross-sectional survey of 1330 participants aged over 40 years (median age 65.8 years) in Chungju, Korea, in 2007. The 324 subjects, who were normotensive in 2003 and who attended a follow-up visit 4 years later, were included in an analysis of the association of serum vitamin D level with the risk of HTN.
Measurements: Serum 25-hydroxy-vitamin D [25(OH)D] and PTH were measured in a central laboratory, using chemiluminescence assays.
Results: The overall prevalence of the MetS in participants of this study was 45.3%. After adjusting for various covariates, subjects in the highest quintile group (61.4-116.8 nmol/l) compared with the lowest quintile group (10.0-29.7 nmol/l) of 25(OH)D had an odds ratio (OR) for having MetS of 0.35 (95% confidence intervals, CI, 0.22-0.56; P for trend <0.001). The median level of 25(OH)D was 46.8 nmol/l among 324 subjects who were normotensive in 2003. After multiple adjustment, the OR was substantially higher for new HTN (OR 2.74; 95% CI 1.40-5.34) in subjects with serum 25(OH)D levels below the median value compared with those above median. The inverse associations of vitamin D and MetS/HTN were unchanged after adjustment for PTH and serum calcium levels. There was no association between PTH and MetS.
Conclusions: We found a strong inverse association of 25(OH)D levels with MetS and HTN in this middle-aged Korean population. Having vitamin D deficiency was associated with an increased risk of having MetS and HTN in this demographic group.