Impaired glucose tolerance, insulin resistance and cardiovascular disease.

Non-insulin-dependent diabetes (NIDDM) is associated with a higher risk of cardiovascular disease (CVD) than in the non-diabetic population. The incidence of CVD is not, however, related to the severity or duration of disease in most studies, suggesting that events in the prediabetic stage can trigger CVD. Several factors have been linked to CVD, including hyperglycaemia, insulin resistance and hyperinsulinaemia. Impaired glucose tolerance (IGT), as defined by the oral glucose tolerance test, is a strong predictor of NIDDM. In addition, IGT and raised glycated haemoglobin levels are possible risk factors for CVD. Hyperinsulinaemia has been associated with increased cardiovascular risk, but this has yet to be confirmed in women. There is also evidence to link insulin resistance with increased cardiovascular risk, although the precise nature of this relationship is unclear. There are many risk factors associated with CVD that are probably working in concert in NIDDM. This makes assessment of risk posed by individual factors, such as hyperglycaemia, hyperinsulinaemia and insulin sensitivity, difficult.