Associations of Vitamin D-Related Biomarkers With Hypertension and the Renin-Angiotensin System in Men and Women.

BACKGROUND: Vitamin D may prevent the development of hypertension through down-regulation of renin-angiotensin system. However, epidemiologic studies assessing the interrelation of vitamin D-related biomarkers with hypertension are sparse. METHODS: We examined the prospective associations between vitamin D-related biomarkers and the risk of hypertension in a nested case-control study. In each of the Women's Health Study (WHS) and Physicians' Health Study (PHS) II, 500 incident hypertension cases and 500 age and race-matched controls were randomly selected. Baseline plasma 25(OH)-vitamin D [25(OH)D], parathyroid hormone (PTH), and total renin concentrations were measured. RESULTS: Among controls, 25(OH)D and PTH were inversely correlated, but neither was correlated with total renin. In the crude model, there was a trend of association between increasing quintiles of 25(OH)D and lower risk of hypertension in women, with relative risks and 95% CIs of 1.00, 1.24 (0.84-1.83), 0.82 (0.53-1.25), 0.75 (0.48-1.16), and 0.81 (0.52-1.27) (P, trend: .07). Adjustment for body mass index and other hypertension risk factors eliminated this association (relative risk of 5th quintile: 1.03). No associations were found in men. Baseline PTH and ratio of 25(OH)D to PTH were not associated with the risk of hypertension in women or men. When men and women were included in the same model, vitamin D insufficiency (defined as 25(OH)D <20 ng/mL) also was not associated with an increased risk of hypertension. No interactions were found across subgroups. CONCLUSIONS: Our study found no association of baseline plasma 25(OH)D or PTH with the risk of hypertension or total renin concentration in middle-aged and older men and women.