Annual incidence and relative risk of diabetes in people with various categories of dysglycemia: A systematic overview and meta-analysis of prospective studies

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 I 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. (c) 2007 Elsevier Ireland Ltd. All rights reserved.