Impact of Coronary Artery Calcium Progression and Statin Therapy on Clinical Outcome in Subjects With and Without Diabetes Mellitus

Coronary artery calcium (CAC) is a marker of atherosclerosis, and CAC progression is independently associated with all-cause mortality in the general population but not convincingly in subjects with diabetes mellitus (DM). The aim of this study was to ascertain the differences in the rates of CAC progression, the effect of statin therapy, and all-cause mortality in subjects with and without DM. The study group consisted of 296 asymptomatic subjects with type 2 DM and 300 controls (mean age 59 ± 6 years, 29% women) who underwent baseline and follow-up CAC scans within a 2-year interval. Absolute annual CAC score change, percentage annual CAC progression(ΔCAC%), event-free survival, and the effect of statin therapy on survival were all assessed. The mean follow-up duration was 56 ± 11 months. Absolute annual CAC score change was 81 ± 10 in subjects with DM and 34 ± 5 in controls (p = 0.0001). Percentage annual CAC progression was 29 ± 9% in subjects with DM and 10 ± 7% in controls (p = 0.0001). The hazard ratios of death in 3 groups of subjects with DM compared to controls without DM were 1.88 (95% confidence interval [CI] 1.51 to 2.36, p = 0.0001) for ΔCAC of 10% to 20%, 2.29 (95% CI 1.56 to 3.38, p = 0.0001) for ΔCAC of 21% to 30%, and 6.95 (95% CI 2.23 to 11.53, p = 0.0001) for ΔCAC >30%, all compared to ΔCAC <10%. The adjusted hazard ratios of all-cause mortality in subjects receiving compared to those not receiving statin therapy were 0.29 (95% CI 0.13 to 0.56, p = 0.001) in those without DM and without CAC progression, 0.51 (95% CI 0.21 to 0.73, p = 0.001) in those with DM and without CAC progression, and 0.71 (95% CI 0.25 to 0.91, p = 0.003) in those without DM and with CAC progression, with all 3 groups compared to 1.0 (reference) in those with DM, with CAC progression and without statin therapy. In conclusion, CAC progression was greater and event-free survival lower in patients with DM compared to controls in proportion to the extent of CAC progression. These results suggest that CAC progression is an independent predictor of all-cause mortality in patients with DM.