Coronary Artery Calcification is Inversely Related to Bone Mineral Density in Young Women:
The CARDIA Study
Coronary artery calcification (CAC), a marker of subclinical atherosclerosis, is related to low bone mineral density (BMD) in postmenopausal women, potentially due to age or declining estrogen levels. Little is known about this association in premenopausal women. During the Year 10 CARDIA Study, BMD was measured by dual energy X-ray absorptiometry at the hip (pelvis, femoral neck, intertrochanteric (IT) region, Ward’s triangle) and the lumbar spine in a subgroup; CAC was measured in a different subgroup by electron beam tomography within the same year. A calcium score was calculated as the product of an area of potential calcification covered by 6 adjacent pixels and the peak CT number within that region; a calcium score >0 indicates the presence of any CAC. Data for both measures were available for 75 women, ages 29-41 years (mean age 35 years). CAC was present in 14.7% of these young women. Mean weight was 75.2±19.1 kg, range 48.6 to 124.4 kg. Mean areal BMD was consistent with the age and reproductive status of these women: 1.18, 0.89, 1.15, and 0.83 g/cm 2 for the pelvis, femoral neck, IT region and Ward’s triangle, respectively; and 1.09 g/cm 2 for the lumbar spine. Cross-sectional logistic regression was performed to determine the crude association between BMD and CAC. BMD was not related to CAC at any site. Weight, however, was strongly associated with CAC, with a prevalence odds ratio (pOR) of 2.53 (95% CI 1.43, 4.49) for a 1-sd increment in weight. When weight was considered as a confounder to the association between BMD and CAC, BMD in the IT region was inversely related to CAC, with a 1-sd (0.17 g/cm 2 ) decrement in the IT region BMD associated with a 233% increase in the odds of CAC (pOR=3.33, 95% CI 1.08, 10.4). This association was not materially affected by adjustment for age, ethnicity, or height. Nearly identical results were seen for CARDIA men, with an inverse association between IT region BMD and CAC after adjustment for weight. These data suggest that in a population-based group of young women with low prevalence of either osteopenia or osteoporosis, lower BMD may be a marker of subclinical atherosclerosis, comparable to findings in postmenopausal women.