Does diabetes have same risk as history of CHD?
Q - What is the evidence that a diagnosis of diabetes carries the same cardiovascular risk as a history of ischaemic heart disease?
A - Diabetes is a major risk factor for cardiovascular disease. Results from the UKPDS study show that reducing conventional modifiable risk factors improves outcome in patients with type one and two diabetes. Furthermore, it is well-known that risk factors cluster, so diabetics are more likely also to be hypertensive and have raised cholesterol.
It is clear that diabetes carries a substantial increase in cardiovascular risk above that caused by the conventional risk factors. The mechanism of this risk is not known, but it is not related simply to glycaemia, and good blood sugar control alone does not seem to reverse the risk.
The precise magnitude of the increased risk is less clear but is almost certainly underestimated. It is probably at least double that predicted by risk calculators or charts, and prescribing thresholds for lipid-lowering treatments or antihypertensives should be adjusted.
It would be wrong to assert that the diagnosis of diabetes always implies a risk equivalent to that of an individual who has already had a cardiovascular event, but in practice, for many
type 2 diabetics doubling their conventional risk score will place them in a similar risk category. The size of potential benefit to be gained by good risk factor control in diabetics is frequently similar to that seen in secondary prevention.
The absolute benefit to be gained from treatment is dependent on the absolute risk of the individual, and for diabetics this is usually high.
Professor Patrick Vallance is director of the Centre for Clinical Pharmacology, Royal Free and University College Medical School, London