Issue 175 Item 9 Pre-Diabetes Doubles the Risk for CVD

Impaired glucose tolerance a major factor, but not so for impaired fasting glucose.

The term "impaired glucose tolerance" (IGT) was originally introduced by the National Diabetes Data Group in 1979 to replace the terms of "borderline diabetes," "latent diabetes," and other categories of glucose intolerance. The definition was based on the evidence that subjects with IGT did not appear to have an increased risk of microvascular disease but were at high risk of developing overt diabetes and might be associated with an increased risk for cardiovascular disease (CVD) and death.
During the last 20 years, a number of studies have shown that the prevalence of CVD as well as mortality from CVD and all causes is higher in subjects with IGT than in those with normal glucose tolerance (NGT). Recently, with the revision of the diagnostic criteria for diabetes and milder degree of hyperglycemia, there is an increased interest in the relationship between nondiabetic glucose levels and CVD risk. The Funagata Diabetes Study revealed that IGT doubled the risk of CVD death compared with NGT, but the risk associated with impaired fasting glucose (IFG) did not increase compared with normal fasting glucose (NFG).

To evaluate the relationship of impaired glucose tolerance (IGT) at baseline to coronary heart disease (CHD) incidence, and cardiovascular disease (CVD) and total mortality at follow-up, and to analyze whether the relationship is independent of the subsequent development of diabetes during follow-up.

A baseline screening survey for diabetes was performed in 1987 using a 2-h 75-g oral glucose tolerance test. A total of 1,234 men and 1,386 women aged 45–64 years, who were free of diabetes at baseline, were followed up for 10 years. During the follow-up, 153 subjects had an incident CHD event, 224 died, and 100 deaths were due to cardiovascular causes. Multivariate adjusted (adjusted for age, sex, waist-to-hip ratio, systolic blood pressure, cholesterol, HDL cholesterol, and smoking) hazard ratio (HR) was estimated using Cox regression analysis.

The results showed that in subjects who had IGT at baseline and who did not progress to diabetes during the follow-up, the multivariate adjusted HR (95% CI) was 1.49 (0.95–2.34) for CHD incidence, 2.34 (1.42–3.85) for CVD mortality, and 1.65 (1.13–2.40) for all-cause mortality.

It has been previously speculated that the risk of CVD associated with IGT might be explained by the fact that people with IGT are at high risk of developing diabetes. Our study demonstrated that IGT at baseline is an independent risk predictor for the incidence of CHD and premature death from CVD and all causes, which was not confounded by the development of clinically diagnosed diabetes during the follow-up.

Baseline IGT was an independent risk predictor for cardiovascular morbidity and mortality and for total mortality, which was not confounded by the subsequent development of overt diabetes.
Diabetes Care 26:2910-2914, 2003

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