Coronary Artery Calcium for the Prediction of Mortality in Young Adults <45 Years Old and Elderly Adults >75 Years Old

Rajesh Tota-Maharaj; Michael J. Blaha; John W. McEvoy; Roger S. Blumenthal; Evan D. Muse; Matthew J. Budoff; Leslee J. Shaw; Daniel S. Berman; Jamal S. Rana; John Rumberger; Tracy Callister; Juan Rivera; Arthur Agatston; Khurram Nasir

Disclosures

Eur Heart J. 2012;33(23):2955-2962. 

In This Article

Results

The mean age of the study population was 54.4 ± 10.7 years. Males comprised 54% of the study population, 37% of patients had a family history of premature CHD, and 14% were smokers at the time of the study. Diabetes mellitus, hypertension, and dyslipidaemia were present in 5, 24, and 30% of the study population, respectively. The proportion of patients with hypertension, diabetes mellitus, and dyslipidaemia increased significantly with the increasing age group, while the prevalence of tobacco use or a positive family history of CHD decreased with increasing age (Table 1, P < 0.0001 for all risk factors mentioned).

The proportion of participants with no CAC in both genders decreased with the increasing age group, from ~70% in the <45-year-old age group to 16% in the ≥75-year-old age group (Figure 1 A, P < 0.0001). Conversely, the percentage prevalence of patients in the CAC = 101–400 and >400 subgroups increased progressively with the increasing age group [Figure 1B; CAC = 101–400: <45 age group 3%, ≥75 age group 25%; CAC > 400: <45 age group 1%, ≥75 age group 36% (P < 0.0001)].

Figure 1.

(A) Gender-based Prevalence of coronary artery calcium with age groups. (B) Prevalence of coronary artery calcium groups with increasing age.

The Kaplan–Meier survival curves demonstrate that within both the <45- and >75-year-old age groups, the increasing CAC group predicted higher mortality (Figure 2A and B). A CAC score of zero predicted a survival of ≥98% over 5.6 years in all age groups studied (Table 2). In the <45-year-old age group, increasing CAC predicted progressively lower survival at mean 5.6-year follow-up (CAC = 0, 99%; CAC = 1–100, 99%; CAC = 101–400, 96%; CAC > 400, 86%). Similarly, in the ≥75-year-old age group, the increasing CAC group predicted a progressively lower survival at mean 5.6-year follow-up (CAC = 0, 98%; CAC = 1–100, 92%; CAC = 101–400, 91%; CAC > 400, 81%).

Figure 2.

(A and B) The Kaplan–Meier survival curves in the <45-year-old and >75-year-old age groups based on the coronary artery calcium group.

Within the <45-year-old age group, MRs increased from 0.7 to 6.8 and 27.6 (per 1000 person-years) as CAC increased from 0 to 100–400 and >400 (Figure 3). When compared with the 2007 US Census Data,[17] patients <45 years old who had CAC ≤ 100 had an MR of 67.3/100 000 (CAC = 0) and 161.9/100 000 (CAC = 1–100), which compares favourably with the national average for this age group (184/100 00). In contrast, CAC = 100–400 and CAC > 400 groups had much higher annual MRs of 683 and 2761 (per 100 000).

Figure 3.

All-cause mortality per 1000 person-years, for each coronary artery calcium category within each age group.

Other age groups demonstrate a similar, though attenuated, increase in all-cause mortality with increasing CAC. In the ≥75-year-old age group, a CAC score of zero was associated with an MR of 2.8/1000 person-years, which is comparable with that of a young person with mild CAC (<45 age group: CAC = 0, 0.6; CAC = 1–100, 1.6).

Increasing CAC independently predicted an increased risk of all-cause mortality among all age groups (Table 3). In the <45-year-old age group, increasing CAC was associated with a 2–34-fold increased risk of all-cause mortality when compared with CAC = 0 [CAC = 1–100, HR 2.3 (95% CI 1.2–4.2); CAC = 101–400, HR 7.4 (95% CI 3.3–16.6); CAC > 400, HR 34.6 (95% CI 15.5–77.4)]. Similarly, in the ≥75-year-old age group, CAC > 400 was associated with 16 times the mortality risk of CAC = 0 [CAC > 400, HR 16.1 (95% CI 5.8–45.1)]. The interaction between the age group and the CAC group on all-cause mortality reached statistical significance (z = −2.48, P= 0.013) and carried a negative value. Thus, the relative risk of death for a given CAC category was slightly lower among the older age groups.

When assessed in separate models, age and CAC categories were responsible for a similar proportion of the overall model variation (z-score: 17.4 for CAC vs. 18.5 for age, P= 0.25). The area under the ROC for CAC (continuous) was higher than the area under the ROC curve for age (continuous) in univariate models fit separately for CAC and age (0.773 vs. 0.745, P= 0.002).

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