Asymptomatic diabetes and cardiovascular risk

The fact that individuals with overt diabetes have increased risks for cardiovascular diseases (CVD) has long been confirmed, but the fact that patients with asymptomatic diabetes are also at high risk for the development of CVD has only been recognised recently. The issue of whether asymptomatic hyperglycaemia is a risk factor for CVD and whether the risk is graded has been debated for at least two decades. Recently, a new surge of interest in the relationship between asymptomatic hyperglycaemia and CVD risk has developed following the recent revision of diagnostic criteria for diabetes and milder degrees of hyperglycaemia in 1997 (1-2).

The most convincing evidence of increased CVD risk related to asymptomatic hyperglycaemia was provided by the DECODE (Diabetes Epidemiology: collaborative analysis Of Diagnostic criteria in Europe) study. In this study, data from 10 prospective European cohort studies including 15388 men and 7126 women aged 30-89 years were collaboratively analysed (3-4). Multivariate Cox proportional hazard analyses showed that the risk for death from all-cause, CVD, coronary heart disease (CHD) and stroke increased significantly in subjects with asymptomatic diabetes defined according to either the fasting plasma glucose 7.0 mmol/l or to the 2-hour post-load plasma glucose ≥11.1 mmol/l. People with impaired glucose tolerance (IGT) also had high risk of death compared with those without IGT, but subjects with impaired fasting glucose (IFG) did not have increased risk of death compared with those with normal fasting glucose levels (3-4). Furthermore, the DECODE study revealed that abnormalities in 2-hour glucose were better predictors of mortality from all cause, CVD and CHD than fasting glucose alone (3-4). A high 2-hour glucose concentration was found to be associated with an increased risk of death, independent of the level of fasting blood glucose, whereas mortality associated with the fasting glucose concentration depended on the level of 2-hour glucose (3).

More recently, we extended the observations of the DECODE study on the predictive value of 2-hour glucose vs fasting glucose with regard to the prediction of the risk of serious incident CHD events (CHD death and non-fatal myocardial infarction) based on five Finnish DECODE study cohorts (5). The data analysis indicated that in subjects without a prior history of diabetes the association of 2-hour glucose with CHD incidence is graded and independent, and that 2-hour glucose is superior to fasting glucose in assessing the risk of future CHD events. Thus, the DECODE study unequivocally confirmed that asymptomatic post-load hyperglycaemia independently increases cardiovascular morbidity and mortality and is a better predictor of the events than fasting hyperglycaemia. These findings are important especially in the elderly population because post-challenge glucose levels increase to a much greater extent with advancing age than fasting glucose. The need for similar assessment regarding mealtime versus fasting glucose and for evaluating the possible benefit of treatments focused on postprandial hyperglycaemia is required, especially in the elderly population.

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.