BACKGROUND

Several estimates of the risk of progression to diabetes in people with impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) have been reported.

OBJECTIVE

To provide an estimate of the risk of progression to diabetes and regression to normoglycemia in these populations.

DESIGN

Systematic overview and meta-analysis of prospective cohort studies published from 1979 until 2004.

SETTING

Global cohort studies.

PATIENTS

People with IFG or IGT detected by a screening oral glucose tolerance test.

MEASUREMENTS

Fasting and post-load plasma glucose levels.

RESULTS

The absolute annual incidence of diabetes in individuals with various categories of IFG or IGT varied from 5 to 10%. Compared to normoglycemic people the meta-analyzed relative risk and 95% confidence interval for diabetes was: 6.35 (4.87-7.82) in people with IGT; 5.52 (3.13-7.91) in people with isolated IGT; 4.66 (2.47-6.85) in people with IFG; 7.54 (4.63-10.45) in people with isolated IFG; and 12.13 (4.27-20.00) in people with both IFG and IGT. People with IGT were 0.33 times as likely to be normoglycemic after 1 year compared to people with normal glucose tolerance (95% CI 0.23-0.43).

LIMITATIONS

Studies that used differing criteria for IFG and IGT were included, and participants were classified on the basis of only one test.

CONCLUSION

IFG and IGT are associated with similar, high relative risk for incident diabetes. The combined abnormality of IFG plus IGT is associated with the highest relative risk.