Table 3. Use of Risk Factors Measured in Early Adult Life to Identify the Population Most at Risk for Developing CAC and Incidence of Coronary Heart Diseasea.
| CAC Screening Strategy in Middle Age | No. (%) | CHD Incidence, No. (%) | CAC Prevalence, No. (%) | Cohort CAC Found by CAC Screening Strategy, No. (%) | No. Enrolled to Find 1 Case of CAC |
|---|---|---|---|---|---|
| Entire eligible cohort | 3330 (100) | 67 (2.0) | 964 (28.9) | 964/964 (100.0) | 3.5 |
| Predicted low CAC risk | 1665 (50.0) | 3 (0.2) | 219 (13.2) | 219/964 (22.7) | 7.7 |
| Predicted high CAC risk | 1665 (50.0) | 64 (3.8) | 745 (44.7) | 745/964 (77.3) | 2.2 |
Abbreviation: CAC, coronary artery calcium.
The probability of developing CAC by ages 32 to 56 years is based on Coronary Artery Risk Development in Young Adults Study cohort risk factors measured twice: when the cohort had a mean age of 25 years (range at year 0 examination, 18-30 years) and 32 years (range at year 7 examination, 25-38 years), using linear regression to predict the development of any CAC at any of the year 15, 20, or 25 examinations (during ages 32-56 years). Risk factors were measured during the year 0 and 7 examinations and included the following: age, race/ethnicity, sex, field center, educational level and both year 0 and 7 smoking status, low-density lipoprotein cholesterol, body mass index, systolic blood pressure, use of antihypertensive medication, use of lipid-lowering medication (both medication categories were rare by year 7: n = 50 antihypertensive medication users, n = 8 lipid-lowering medication users), and type 1 or 2 diabetes (also rare by year 7: n = 37). The prediction formula and observed CAC by deciles of the CAC prediction are presented in the eAppendix, eTable 4, and eTable 5 in the Supplement.