Relationships between vascular calcification, calcium metabolism, bone density, and fractures.

Factors involved with calcium metabolism, such as serum calcium and phosphate and calcium intake, have been associated with vascular disease in different populations. We investigated whether this association is mediated via increased vascular calcification by assessing relationships between these factors and abdominal aortic calcification (AAC) and coronary artery calcification (CAC). A total of 1471 healthy postmenopausal women participated in a 5-year randomized, placebo-controlled trial of calcium 1 g/day, and 323 healthy middle-aged and older men participated in a 2-year randomized, placebo-controlled trial of calcium 600 or 1200 mg/day. AAC was assessed on vertebral morphometric images at baseline and follow-up. Based on computed tomography, 163 men had CAC assessed, on average, 1.5 years after study completion. In elderly women, AAC was positively related to serum calcium (p < .001), phosphate (p = .04), and the calcium-phosphate product (p = .003), but changes in AAC over time and incidence of cardiovascular events were not related to these variables. In middle-aged men, AAC and CAC were not consistently related to these variables. Neither dietary calcium intake nor calcium supplementation was associated with changes in the prevalence of AAC over time, and calcium supplementation also was not related to CAC scores in men. After adjusting for age, AAC was not associated with low bone mineral density (BMD) at baseline, changes in BMD over time, or fracture incidence. CAC also was not related to baseline BMD. In summary, serum calcium and phosphate are associated with AAC in older women, but dietary calcium intake and calcium supplementation were not associated with changes in AAC over 2 to 5 years.