Objective: In type 2 diabetes mellitus (T2DM), it remains unclear whether coronary artery calcium (CAC) provides additional information about cardiovascular disease (CVD) mortality beyond the Framingham Risk Score (FRS) factors.
Research design and methods: A total of 1,123 T2DM participants, ages 34-86 years, in the Diabetes Heart Study followed up for an average of 7.4 years were separated using baseline computed tomography scans of CAC (0-9, 10-99, 100-299, 300-999, and ≥1,000). Logistic regression was performed to examine the association between CAC and CVD mortality adjusting for FRS. Areas under the curve (AUC) with and without CAC were compared. Net reclassification improvement (NRI) compared FRS (model 1) versus FRS+CAC (model 2) using 7.4-year CVD mortality risk categories 0% to <7%, 7% to <20%, and ≥20%.
Results: Overall, 8% of participants died of cardiovascular causes during follow-up. In multivariate analysis, the odds ratios (95% CI) for CVD mortality using CAC 0-9 as the reference group were, CAC 10-99: 2.93 (0.74-19.55); CAC 100-299: 3.17 (0.70-22.22); CAC 300-999: 4.41(1.15-29.00); and CAC ≥1,000: 11.23 (3.24-71.00). AUC (95% CI) without CAC was 0.70 (0.67-0.73), AUC with CAC was 0.75 (0.72-0.78), and NRI was 0.13 (0.07-0.19).
Conclusions: In T2DM, CAC predicts CVD mortality and meaningfully reclassifies participants, suggesting clinical utility as a risk stratification tool in a population already at increased CVD risk.