Vitamin D deficiency is associated with an increased risk of new-onset coronary artery calcification (CAC), a finding that may help to explain why cardiovascular events and death are more likely in individuals with low vitamin D levels, researchers reported.

Researchers led by Ian H. de Boer, MD, of the University of Washington in Seattle studied 1,370 individuals, of whom 394 had CKD and 976 did not. At baseline, CAC was present in 723 subjects (53%).

During three years of follow-up, CAC developed in 135 (21%) of the 647 subjects who did not have CAC at baseline. Lower levels of 25-hydroxyvitamin D were was associated with an increased risk of new-onset CAC.

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Compared with subjects who had a 25-hydroxyvitamin D level of 15 ng/mL or higher, those with lower levels had a 38% increased risk of new-onset CAC after adjusting for numerous potential confounders, including BP, diabetes, total and HDL cholesterol, and triglycerides.

Furthermore, each 10 ng/mL decrease in 25-hydroxyvitamin D was associated with a 23% increased risk of developing CAC. The investigators published their findings in the Journal of the American Society of Nephrology (2009;20:1805-1812).

The concentration of 25-hydroxyvitamin D was not associated with prevalent CAC at baseline, the investigators reported.

The association of lower 25-hydroxyvitamin D levels with new-onset CAC seemed to be stronger in subjects with impaired renal function, but it was not significantly different from individuals without impaired renal function, the investigators reported.

They noted that vitamin D deficiency is associated with an increased risk of cardiovascular disease (CVD) and death, but the nature of this association has been unclear.

“These results suggest that accelerated development of coronary atherosclerosis may underlie, in part, the increased cardiovascular risk associated with vitamin D deficiency,” the authors wrote.

The researchers observed that relationship of lower 25-hydroxyvitamin D levels with an increased risk of CAC was independent of established risk factors for atherosclerosis, such as diabetes, smoking BP, dyslipidemia, BMI, and C-reactive protein. “This suggests that vitamin D deficiency may be related to CVD through unique biologic pathways,” they noted.

CAC was quantified using an electron-beam CT scanner or a multidetector CT system. A radiologist or a cardiologist blinded to clinical data read all CT scans.