Vascular calcification and 25-hydroxyvitamin D levels in non-dialysis patients with chronic kidney disease stages 4 and 5

Background. Cardiovascular disease (CVD) is the leading cause of death among chronic kidney disease (CKD) patients. Vascular calcification is highly prevalent in this population and is an independent predictor of cardiovascular mortality. Vascular calcification in uraemic patients is known to be an active and regulated process subject to the action of many promoting and inhibitory factors. The role of vitamin D in this process remains controversial. We evaluated the relationship between serum levels of 25-hydroxyvitamin D (25(OH) D) and vascular calcification evaluated by plain X-ray images, in predialysis patients with CKD stages 4 and 5. Methods. We performed a cross-sectional study with 210 CKD patients stages 4 and 5 managed at our predialysis unit. Patients were 63.5 +/- 13 years of age, 60.5% males, 64.8% diabetics and 47.1% with a history of CVD. Plain X-ray images of pelvis, hands and lateral lumbar spine from all subjects were studied for calculation of semiquantitative vascular calcification scores as described by Adragao and Kauppila. Results. We found a high prevalence of vascular calcification in our population. Adragao scores revealed only 47 patients (22.4%) without vascular calcification and 120 (57.1%) with scores higher than 3. Kauppila scores revealed only 29 patients (13.8%) without aortic calcifications and 114 patients (54.3%) with scores higher than 7. Higher vascular calcification scores were related to older age, diabetes, history of CVD and lower levels of 25(OH) D. Only 18.5% of patients had adequate levels of 25(OH) D (> 30 ng/mL), 53.7% of them had insufficient levels (15-30 ng/mL) and 27.8% had deficient levels (< 15 ng/mL). Multivariate analysis showed that age, diabetes and CVD were directly associated and 25(OH) D levels were inversely associated with vascular calcifications. Conclusions. Our results show an independent and negative association between serum levels of 25(OH) D and vascular calcification. Further and larger prospective studies are needed to clarify the possible role of vitamin D deficiency in the development of vascular calcification in CKD patients.