Differences in association of bone mineral density with coronary artery calcification in men and women: the Rancho Bernardo Study

Objective: Whether osteoporosis and calcification of atherosclerotic plaque are two independent, age-related processes or linked by similar mechanisms of bone mineralization and plaque calcification is unknown. This study examines the sex-specific association between bone mineral density (BMD) and coronary artery calcification with a particular focus on hormone therapy (HT). Design: Participants were 180 men (aged 47-86 years) and 186 women (aged 58-81 years) without a history of heart disease who had hip and spine BMD assessed by dual-energy x-ray absorptiometry and coronary artery calcium score (CACS) measured by electron-beam computed tomography. Calcium scores were categorized into none/minimal (<= 10), mild (11 - 100), moderate (101-399), and severe (>= 400). Ordinal and binary logistic regressions examined the associations between site-specific BMD and CACS. Results: In men and women not using HT, there was no age-independent association between BMD at any site and CACS. In contrast, among current HT users an inverse association of BMD with coronary artery calcification was observed at the total hip (odds ratio [OR] = 0.56, 95% Cl, 0.33-0.95), trochanter (OR = 0.55, 95% Cl, 0.32-0.93), and intertrochanter area (OR = 0.60, 95% Cl, 0.41-0.86) after adjustment for age and other risk factors. Other skeletal sites showed similar, but not statistically significant, associations (P < 0.1). n Conclusion: Lack of association between BMD and CACS in men and women not using HT and the inverse association in women on HT suggest that the association between coronary and bone calcium might be mediated by estrogen.