Associations between calcium-phosphate metabolism and coronary artery calcification; a cross sectional study of a middle-aged general population

Background and aims: High serum calcium-phosphate levels are associated with increased risk of cardiovascular disease (CVD) in patients with chronic kidney disease. Recent studies have demonstrated this relationship also in subjects with normal kidney function. Our aim was to examine whether calcium-phosphate metabolism is associated with the presence and extent of coronary artery calcification (CAC) in asymptomatic and apparently healthy individuals. Methods: Serum samples from 1088 randomly recruited middle-aged men and women without known CVD and diabetes (DM), from the general population, were analysed for total calcium, phosphate, parathyroid hormone (PTH) and 25-hydroxyvitamin D (25(OH)D). CAC was measured by a non-contrast cardiac CT scan and categorised into four groups: 0, 1-99, 100-399, ≥400 Agatston units. The association of calcium-phosphate metabolism with CAC was evaluated by a multiple ordered logistic regression model. All the multiple regression analyses were performed in the entire cohort as well as in men and women separately. Results: In the study population, 96% of the serum calcium values, 93% of the PTH values, 90% of the phosphate values, and only 64% of the 25(OH)D values were placed within the normal range.In men, the odds of being in a higher CAC category, i.e. having more severe CAC, increased by 30% when serum calcium concentration increased by 0.1 mmol/l (95% CI: 1.04-1.61, p = 0.019), independently of traditional cardiovascular risk factors. In women, no significant association between serum calcium and CAC was identified (OR 0.99, 95% CI: 0.81-1.21, p = 0.91). Neither phosphate, PTH nor 25(OH)D was significantly associated with CAC in men, in women or when performed in the entire cohort. Conclusions: Serum calcium, even with values within normal range and independent of traditional risk factors, was significantly associated with CAC in asymptomatic and apparently healthy middle-aged men, but not in women.