Vitamin D affects survival independently of vascular calcification in chronic kidney disease

Abstract

Background and objectives: Cardiovascular disease is the main cause of mortality in chronic kidney disease (CKD) patients. Vitamin D might have beneficial effects on vascular health. The aim of this study was to determine the prevalence of vitamin D deficiency (25-hydroxyvitamin D [25D] <or= 15 ng/ml) and insufficiency (25D levels between 16 and 30 ng/ml) in a cohort of patients at different CKD stages and the relationships between vitamin D serum levels, vascular calcification and stiffness, and the mortality risk.

Design, setting, participants & measurements: One hundred forty CKD patients (85 men, mean age 67 +/- 12 yr; CKD stages 2 [8%], 3 [26%], 4 [26%], 5 [7%], and 5D [(33%]) were allocated for a prospective study. Serum levels of 25D and 1,25-dihydroxyvitamin D, aortic calcification score, and pulse wave velocity (PWV) were evaluated.

Results: There was a high prevalence of vitamin D deficiency (42%) and insufficiency (34%). Patients with 25D <or= 16.7 ng/ml (median) had a significantly lower survival rate than patients with 25D >16.7 ng/ml (mean follow-up, 605 +/- 217 d; range, 10 to 889; P = 0.05). Multivariate adjustments (included age, gender, diabetes, arterial pressure, CKD stage, phosphate, albumin, hemoglobin, aortic calcification score and PWV) confirmed 25D level as an independent predictor of all-cause mortality.

Conclusions: Vitamin D deficiency and insufficiency were highly prevalent in this CKD cohort. Low 25D levels affected mortality independently of vascular calcification and stiffness, suggesting that 25D may influence survival in CKD patients via additional pathways that need to be further explored.

Figures

Figure 1.

A) Serum levels of 25-hydroxyvitamin D (25D) and (B) serum levels of 1,25-dihydroxyvitamin D (1,25D) as a function of CKD stage (with dashed lines indicating the reference values). *P < 0.05 for CKD stage 5D versus other groups.

Figure 2.

Crude patient survival as a function of vitamin D (25D) levels (≤16.7 ng/ml or >16.7 ng/ml).