Background: Vascular disease is a leading cause of morbidity and mortality in diabetes mellitus (DM). It is uncertain whether pre-diabetes (impaired fasting glucose [IFG]) increases risk for subclinical vascular disease.

Methods: Cardiovascular disease (CVD) risk factors and carotid artery structure (wall thickness [IMT] and vascular mass) and presence and extent of atherosclerosis were compared in 2461 Strong Heart Study participants free of prevalent CVD: 1038 with normal fasting glucose (NFG), 254 with IFG (110–125 mg/dl), and 1169 with DM.

Results: Participants with IFG were more obese and had lower HDL cholesterol than those with NFG but were comparable in other CVD risk factors. Participants with DM were more likely to be female, hypertensive, non- smoking, and to have higher triglycerides than the other two groups. Following adjustment for differences in CVD risk factors, DM had greater carotid IMT (0.75 mm), mass (16.38 mm²) and presence (69.1%) and extent (log transformed plaque score: 0.78) of atherosclerosis compared to NFG and IFG. NFG and IFG had comparable adjusted IMT (0.73 vs. 0.73 mm), arterial mass (15.51 vs. 15.67 mm²), plaque (58.8 vs. 58.5 %) and plaque score (0.64 vs. 066).

Conclusions: Other than elevated fasting glucose, the distinguishing features of IFG are obesity and reduced HDL cholesterol (comparable to DM). Greater degrees of arterial hypertrophy and atherosclerosis are seen in DM but not IFG. These findings have implications for public health efforts to identify individuals with IFG and intervene to limit progression to the vascular disease associated with DM.