Comparison Between Diabetes Incidence using Different Cut Points of IFG: Tehran Lipid Glucose Study (TLGS)

In 2003, the American diabetes Association (ADA) recommended that the definition for a cut off of impaired fasting glucose (IFG) should be changed to 100- 125 mg/dl. This study has examined the effect of different cut points for IFG on diabetes incidence in Tehran's urban population. A total of 4929 (non-diabetic adults), aged 20-86 years, participants of the Tehran Lipid Glucose Study, were followed for diabetes incidence (based on FBS and glucose tolerance tests) for 3.5 years and were divided into various groups, normoglycemia < 100, original IFG 110-125, added IFG 100-110 and new IFG100-125 mg/dL. Odds ratio for diabetic incidence after adjustment for confounding factors with logistic regression model was measured. The mean ages were 42.9±13.7 (minimum 20 & maximum 86 years old) 59.1% of participants were female (n= 2916). Prevalences of original IFG, added IFG and new IFG were 3.7% (n=183), 11.8% (n= 584), 15.5% (n= 767) respectively. At the end of study, 188 cases (3.8%) were diabetic. Incidence of diabetes in the normoglycemia, original IFG, added IFG and new IFG groups were 1.8% (n= 76), 26.2% (n= 48), 11% (n= 64), and 14.6% (n= 112) respectively. Odds ratios for diabetes incidence after adjustment for age/sex and confounding factors compared with normglycemia, diabetes incidence were 11.4 (7.4-17.6), 4.7 (3.3-6.8), 6.3 (4.5-8.5) for original IFG, added IFG, and new IFG respectively. The new IFG definition does not appear to have enhanced ability to predict diabetes incidence compared to the original IFG definition.