The MESA sample for this analysis comprised 6,698 adults age 45–84 years at baseline (3,161 men, 3,537 women). Over 23,735 person-years of follow-up, we identified incident 222 CVD events (159 CHD [61 myocardial infarction, 81 angina, 3 resuscitated cardiac arrest, 13 CHD deaths]; 59 stroke, of whom 3 also had a CHD event; and 7 other atherosclerotic CVD deaths). Fifty percent of the MESA sample had detectable CAC. The mean ± SD value for ln(CAC±1) was 2.2 ± 2.5, for maximum internal carotid IMT was 1.07 ± 0.60 mm, for maximum common carotid IMT was 0.87 ± 0.19 mm and for Z score maximum IMT was 0.00 ± 1.00.
As shown in , the three measures of carotid IMT were all positively associated with incident CVD, with age, race/ethnicity, and sex-adjusted HRs for the highest versus lowest quartile of 3.3 (95% CI 2.1–5.2) for the maximum internal carotid IMT, 2.3 (95% CI 1.4–3.8) for the maximum common carotid IMT, and 3.8 (95% CI 2.2–6.4) for the Z score maximum IMT (all p<0.0001). The remaining IMT analyses therefore focused on Z score maximum IMT. For CAC (), the HRs of CVD increased across categories, the age, race/ethnicity, and sex-adjusted HR being 6.0 (95% CI 3.9–9.1) for the highest CAC quartile versus zero CAC (p<0.0001). The results for CHD risk (not shown) were similar. For reference to recommended clinical cutpoints for CAC,1,3
the age, race/ethnicity, and sex-adjusted HRs (95% CIs) for CAC scores of 0, 1–99,100–399, and ≥400 were 1.0, 4.7 (95% CI 2.5–8.7), 11.5 (95% CI 6.2–21.5), and 16.1 (95% CI 8.5–30.8), respectively (not shown in tables).
Hazard Ratios (HRs) and 95% Confidence Intervals (CI) for an Incident Cardiovascular Disease Event in Relation to Quartiles of Maximal Carotid Intima-Media Thickness (IMT) or Coronary Artery Calcium (CAC), MESA, 2000 to 2004
When put in the same model, CAC was more strongly associated than was IMT with both CVD and CHD (). The multivariable adjusted HRs (95% CI) of CVD and CHD per standard deviation increment were 2.1 (1.8–2.5) and 2.5 (2.1–3.1), respectively, for ln(CAC + 1), compared with 1.3 (1.1–1.4) and 1.2 (1.0–1.4) for Z score maximum IMT. Furthermore, the Z statistics were larger and p-values were smaller for the CAC association. In contrast, for stroke, only Z score maximum IMT was statistically significant (p<0.05) with multivariable-adjusted hazard ratio of 1.3 (1.1–1.7) while the hazard ratio for ln(CAC + 1) was 1.1 (0.8–1.4).
Table 2 Hazard Ratios (HRs) and 95% Confidence Intervals (CI) for an Incident Cardiovascular Disease (CVD), Coronary Heart Disease (CHD), or Stroke Event in Relation to One Standard Deviation (SD) Increment of Maximal Carotid Intima-Media Thickness (IMT) or Coronary (more ...)
A categorical analysis () also suggested CAC predicted incident CVD and CHD better than did IMT. For example, the multivariable-adjusted HRs of CHD for the highest quartile versus lowest 50th percentile were 8.2 (95% CI 4.5–15.1, p<0.0001) for CAC and 1.7 (95% CI 1.1–2.7, p=0.01) for IMT.
Table 3 Hazard Ratios (HRs) and 95% Confidence Intervals (CI) for an Incident Cardiovascular Disease (CVD), Coronary Heart Disease (CHD), or Stroke Event in Relation to Quartiles of Maximal Carotid Intima-Media Thickness (IMT) or Coronary Artery Calcium (CAC), (more ...)
In supplemental analysis, we restricted to subjects at intermediate CHD risk, based on a Framingham risk score of 1–2% per year (n = 1841, with 54 CHD events). Among them, the multivariable adjusted HRs (95% CI) of CHD per standard deviation were 2.4 (1.7–3.3, p<0.0001) for ln(CAC + 1) and 1.3 (1.0–1.6, p<0.05) for Z score maximum IMT when both were included in the model. In the same subgroup at intermediate Framingham risk, for CVD (81 events), the multivariable adjusted HRs were 1.8 (1.4–2.2, p<0.0001) for ln(CAC+1) and 1.4 (1.1–1.6, p=0.001) for Z score maximum IMT.
shows crude rates of incident CVD by 9 joint categories of Z score maximum IMT and CAC. Rates of CVD were between 1–2% per year for those with (1) a moderate level of CAC and high IMT or (2) a high level of CAC and low IMT. CVD rates were >2% per year for those with a high level of CAC and either a moderate or high level of IMT. Those with zero CAC and either low or moderate IMT had almost no events during this follow-up period. Findings for CHD were similar (not shown).
ROC analysis suggested CAC score predicted CVD incidence better than did carotid IMT. With the multiple risk factors in the model for CVD, the area under the curve (AUC) was 0.772 (95% CI 0.74–0.80). After then adding Z score maximum IMT the AUC was 0.782 (95% CI 0.75–0.81); after substituting CAC score for IMT was 0.808 (95% CI 0.78–0.83); and after including both IMT and CAC was 0.811 (0.78–0.84). A similar ROC analysis for CHD produced AUCs of 0.771 (95% CI 0.74–0.80) for risk factors alone, 0.782 (95% CI 0.75–0.82) for risk factors plus IMT, 0.823 (95% CI 0.79–0.85) for risk factors plus CAC, and 0.824 (95% CI 0.79–0.85) for risk factors plus CAC and IMT.