Impaired fasting glycaemia and undiagnosed diabetes: prevalence, cardiovascular and behavioural risk factors.

Background: Early discovery of type 2 DM (NIDDM) is essential. The diagnostic criteria of DM have been recently modified (FBG 126 vs 140 mg/dl) and the characteristics of undiagnosed subjects in large populations must be defined. At the same time subjects with impaired FBG need to be studied mainly for their cardiovascular complications.

Methods: During 14 months, 61,724 male and female subjects (mean age 40) were explored in the French Institute for Health Protection (I.R.S.A). Clinical data, FPG, CV risk factors and dietary habits collected. Cut-off value for FPG: 110-125 mg/dl (IFG) (G2), 126-139 mg/dl defining undiagnosed diabetes with no history of diabetes. Subjects with FPG >=140 mg/dl (G4) former ADA/WHO criteria for diabetes and with the new criteria (FPG: 126-139 mg/dl) (G3) were compared to IFG (G2) and controls<110 mg/dl (G1).

Results: With the new criteria (>=126 mg/dl) the prevalence of unknown diabetes in the cohort was 1.2% accounting for 41% of the overall prevalence of the disease (known + unknown). This is nearly 2.5 times more than with the previous criteria, > 140 mg/dl, (1.2 vs 0.5%). In G2/G1 and G3/G2 highest FPG had higher BMI, H/W ratio, heart rate (male only G3/G2), BP, gamma GT (role of alcohol in males), uric acid and TG. A role of absence of breakfast, low dairy products consumption is found. No difference between G4 and G3 found.

Conclusion: These results support the new criteria of FPG 126 mg/dl and suggest that it would be necessary to investigate and prevent cardiovascular risk factors as soon as fasting glycaemia is found to be over 110 mg/dl. Nutritional and behavioural education should be given at this early stage of the disease.