Impaired fasting glucose: How low should it go?

OBJECTIVE- Impaired fasting glucose (IFG) has been recently introduced as a stage of abnormal carbohydrate metabolism, but the evidence on which its g lucose limits (fasting plasma glucose [FPG] 6.1-6.9 mmol/l) are based is no t strong. The aim of this study was to determine if 6.1 mmol/l represents a clear cutoff in terms of the risk of future diabetes and in terms of eleva ted cardiovascular risk factor levels, and to examine the use of other lowe r limits of IFG. RESEARCH DESIGN AND METHODS- A population-based survey of the island of Mau ritius was undertaken in 1987, with a follow-up survey 5 years later. On bo th occasions, an oral glucose tolerance test was performed and cardiovascul ar risk factors were measured. RESULTS- Data were available from 4,721 nondiabetic people at baseline, and from 3,542 at follow-up. At baseline, blood pressure, lipids, and obesity increased in a linear fashion with increasing FPG, with no evidence of a th reshold effect. The risk of developing hypertension at follow-up was greate r for those people with baseline FPG greater than or equal to 6.1 mmol/l (P < 0.001), The risk of developing diabetes at follow-up increased with incr easing baseline FPG, but there was little evidence of a threshold near 6.1 mmol/l. CONCLUSIONS- Cardiovascular risk and risk of future diabetes increase conti nually with increasing FPG, and there is no threshold value on which to bas e a definition of IFG. If a lower limit of similar to 5.8 mmol/l is used, t he category defines a group more similar to the group with impaired glucose tolerance, with regard to total prevalence and the risk of subsequent diab etes.