Is glycaemia or insulin dose the stronger risk factor for coronary artery disease in type 1 diabetes?

Although coronary artery disease (CAD) is the leading cause of death in type 1 diabetes (T1D), the mechanisms responsible for the greatly increased risk are poorly understood. In particular, the role of glycaemic control is controversial with one study suggesting it predicts CAD mortality but not incidence. In this analysis, of the Pittsburgh Epidemiology of Diabetes Complications study cohort of T1D, we examine whether risk factors differ for CAD morbidity and mortality, with a specific focus on HbA1c and insulin dose. Participants (n=592) were followed for 18 years for incident non-fatal and fatal CAD. Cox stepwise regression was used to determine the independent risk factors for non-fatal and fatal CAD. Mean age and diabetes duration at study baseline were 29 and 20 years, respectively. There were 109 incident non-fatal and 48 fatal CAD events. Baseline HbA_1C was an independent risk factor for fatal CAD, along with duration of diabetes and albuminuria. In contrast, baseline lower insulin dose was strongly predictive of non-fatal CAD, as was lower renal function, higher diastolic blood pressure, and lipids. HbA_1C predicts CAD mortality while lower insulin dose and standard CAD risk factors predict CAD morbidity.