Atherosclerosis 190 (2007) 224–231 Coronary artery calcium score, risk factors, and incident coronary heart disease events Timothy S. Church a,∗ , Benjamin D. Levine b,c , Darren K. McGuire c , Michael J. LaMonte a , Shannon J. FitzGerald a , Yiling J. Cheng a , Thomas E. Kimball d , Steven N. Blair a , Larry W. Gibbons d , Milton Z. Nichaman a a The Cooper Institute, Dallas, TX, United States b Institute for Exercise and Environmental Medicine and Presbyterian Hospital, Dallas, TX, United States c University of Texas Southwestern Medical Center, Dallas, TX, United States d Cooper Clinic, Dallas, TX, United States Received 6 July 2005; received in revised form 22 November 2005; accepted 1 February 2006 Available online 15 March 2006 Abstract Background: Whether the absence of coronary artery calcium, or conversely the presence of high volumes of coronary artery calcium, may alter assessment of coronary heart disease risk based on traditional risk factors is uncertain. We sought to identify a potential threshold of coronary artery calcium for clinical use and examine the predictive power of coronary artery calcium in individuals categorized using conventional coronary heart disease risk assessment. Methods: The study included 10,746 men and women (36.3%) with a mean age of 53.8 ± 9.9 years who were either physician- or self- referred for electron beam tomography scanning to a preventive medical clinic. Coronary heart disease risk factors were elicited by use of a questionnaire. Results: During a mean follow-up of 3.5 years, 81 primary events (coronary heart disease death or nonfatal myocardial infarction) occurred. Among individuals with a coronary artery calcium score of zero, the primary event rate was very low (0.4 events per 1000 person-years of observation). When participants were stratified by self-reported coronary heart disease risk factors (0–2, or 3–4), a coronary artery calcium score ≥100 was associated with substantially increased risk of coronary heart disease events within each level of stratification. In a subgroup of participants with available clinical data, similar results were found when participants were categorized by Framingham risk scores. Conclusions: Coronary artery calcium score can identify individuals at increased risk for coronary heart disease events who otherwise would be considered low-risk based on clinical assessment. A coronary artery calcium score of zero is associated with very low risk for coronary heart disease in the short to intermediate term (≈3.5 years) regardless of the number of risk factors present. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Calcium; Coronary disease; Prevention 1. Introduction Electron beam tomography has the sensitivity to detect and quantify small amounts of coronary artery calcium ∗ Corresponding author at: The Cooper Institute, 12330 Preston Road, Dallas, TX 75230, United States. Tel.: +1 972 341 3252; fax: +1 972 341 3225. E-mail address: tchurch@cooperinst.org (T.S. Church). (CAC) and has been used with increasing frequency to assess the extent of coronary atherosclerosis [1,2]. A positive qualitative and quantitative association between CAC and clinically manifest coronary heart disease (CHD) has been demonstrated in numerous cross-sectional studies and a few prospective studies [3–16]. However, a number of important issues in regard to the clinical utility of CAC measurement remain unresolved. If CAC is a measure of atherosclerotic burden, it remains to be determined if CAC scores will iden- 0021-9150/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.atherosclerosis.2006.02.005