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 glucose limits (fasting plasma glucose [FPG] 6.1-6.9 mmol/l) are based is not 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 elevated cardiovascular risk factor levels, and to examine the use of other lower limits of IFG.


METHODS
A population-based survey of the island of Mauritius was undertaken in 1987, with a follow-up survey 5 years later. On both occasions, an oral glucose tolerance test was performed and cardiovascular 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 threshold effect. The risk of developing hypertension at follow-up was greater for those people with baseline FPG > or =6.1 mmol/l (P<0.001). The risk of developing diabetes at follow-up increased with increasing baseline FPG, but there was little evidence of a threshold near 6.1 mmol/l.


CONCLUSIONS
Cardiovascular risk and risk of future diabetes increase continually with increasing FPG, and there is no threshold value on which to base a definition of IFG. If a lower limit of approximately 5.8 mmol/l is used, the category defines a group more similar to the group with impaired glucose tolerance, with regard to total prevalence and the risk of subsequent diabetes.
Shaw
J E
JE
International Diabetes Institute, Melbourne, Australia. jshotham@hotmail.com
Zimmet
P Z
PZ
Hodge
A M
AM
de Courten
M
M
Dowse
G K
GK
Chitson
P
P
Tuomilehto
J
J
Alberti
K G
KG
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis* / Q000378:metabolism; D001794:Blood Pressure; D002318:Cardiovascular Diseases / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000453:epidemiology*; D005215:Fasting; D005951:Glucose Tolerance Test; D006801:Humans; D006973:Hypertension / Q000453:epidemiology; D008055:Lipids / Q000097:blood; D008436:Mauritius / Q000453:epidemiology; D008875:Middle Aged; D009765:Obesity / Q000097:blood; D012372:ROC Curve; D044469:Racial Groups; D012016:Reference Values; D012307:Risk Factors
D001786:Blood Glucose; D008055:Lipids