Non-diabetic hyperglycaemia and cardiovascular risk: moving beyond categorisation to individual interpretation of absolute risk

Non-diabetic hyperglycaemia is usually not considered at all or is viewed as a binary risk category in isolation from other factors when quantifying cardiovascular risk. We argue that hyperglycaemia should be considered as a continuous risk factor and only in the context of other vascular risk factors. To examine the potential impact of hyperglycaemia on cardiovascular disease (CVD) risk, we calculated the absolute CVD risk in groups defined by different levels of HbA(1c) and other CVD risk factors. We used data on 10,144 men and women from the European Prospective Investigation of Cancer-Norfolk cohort to calculate CVD rates across levels of HbA(1c) in groups characterised by different levels of traditional risk factors. We found significant differences in CVD rates across levels of HbA(1c) in groups defined by different levels of the other risk factors. CVD rates for non-diabetic individuals with an HbA(1c) of < 5.5% increased from 0.6 (95% CI 0.3-1.2) to 29.6 (95% CI 14.8-59.1) per 1,000 person-years when traditional CVD risk factors were added sequentially to the lowest risk reference group. In most cases, non-diabetic individuals with an HbA(1c) of < 5.5% and high values for all other CVD risk factors had substantially higher absolute CVD rates than those with an HbA(1c) of 6.0% to 6.4% but with no other raised CVD risk factors (29.6 [95% CI 14.8-59.1] and 2.5 [95% CI 0.4-18.1], respectively). A history of diabetes significantly increased CVD risk over the non-diabetic hyperglycaemia range. Comparisons of CVD rates across tertiles of total cholesterol:HDL-cholesterol ratio or mean systolic blood pressure in groups characterised by different levels of other risk factors showed similar findings. In people with non-diabetic hyperglycaemia, cardiovascular risk is highly dependent on the presence of other CVD risk factors. Attention should be given not to whether an individual has 'pre-diabetes', 'hypertension' or 'hypercholesterolaemia', but to an integrated assessment of CVD risk, based on the combination of risk factors present and potential benefits of treatment.