Diabetes as a coronary artery disease risk equivalent: before a change of paradigm?

Current guidelines consider diabetes per se as a coronary artery disease (CAD) risk equivalent. We aimed at investigating the contribution of baseline coronary atherosclerosis to the risk of diabetic patients for future vascular events.

Prospective cohort study.

Vascular events were recorded over 4 years in 750 consecutive patients undergoing coronary angiography for the evaluation of stable CAD.

From our patients, 244 had neither type 2 diabetes (T2DM) nor significant CAD (i.e. coronary stenoses >or=50%) at the baseline angiography, 50 had T2DM but not significant CAD, 342 did not have T2DM but had significant CAD, and 114 had both T2DM and significant CAD. Nondiabetic patients without significant CAD had an event rate of 9.0%. The event rate was similar in T2DM patients without significant CAD (8.0%, P = 0.951), but higher in nondiabetic patients with significant CAD (24.9%, P<0.001). Patients with T2DM and significant CAD had the highest event rate (43.0%). Importantly, T2DM patients without significant CAD had a significantly lower event rate than nondiabetic patients with significant CAD (P = 0.008).

T2DM per se is not a CAD risk equivalent. Moderate-risk diabetic patients without significant CAD and very high-risk diabetic patients with significant CAD add up to a grand total of high-risk diabetic patients, this is why diabetes seems to be a CAD risk equivalent in many epidemiological studies.