Background: Although African Americans have a lower prevalence and extent of coronary artery calcium (CAC) than whites, the relationship between ethnicity and CAC progression is unknown. In a prospective rescan substudy of the Prospective Army Coronary Calcium (PACC) Project, we evaluated ethnic differences in the rates of CAC progression over 4 years.
Methods: Two hundred healthy male PACC Project participants (age, 47.8 +/- 2.8 years) with CAC on their original scan volunteered to undergo a second electron beam tomography (EBT) scan and cardiovascular risk factor assessment (interscan interval, 4.3 +/- 1.2 y). All results were independently examined and blinded to baseline data. A change in CAC score >or=15%/y was defined as clinically significant progression. The relationship between race and CAC progression was evaluated with multivariable linear and logistic regression models controlling for age and other cardiovascular risk factors.
Results: African Americans had significantly lower baseline CAC scores (34.3 vs 101.5; P = 0.004); lower follow-up CAC scores (56.6 vs 180.6; P = 0.001); and worse cardiovascular risk profiles. The annualized CAC progression rate was not significantly related to race in the multivariable linear regression model controlling for age, the Framingham risk score, and other cardiovascular risk factors. Significant CAC progression occurred in 43.5% of all participants. The incidence of significant progression of CAC for African American and white men was similar (53.1% vs 52.4%; P = 0.94), even when controlling for age, the Framingham risk score, and other cardiovascular risk factors.
Conclusion: Although African American men have less CAC than white men, CAC progression occurs at a comparable rate over 4 years.