Aims: The aim of this study was to estimate the conversion rate to normal glucose tolerance (NGT) from a state of abnormal glucose metabolism and to identify characteristics predicting the conversion rate in first-degree relatives (FDRs) of patients with type 2 diabetes with glucose intolerance.

Methods: A total of 2368 (614 men and 1754 women) FDRs of consecutive patients with type 2 diabetes aged 20-70 years in 2003-2005 were followed through 2007. Glucose tolerance classification was based on the criteria of the American Diabetes Association base on standard 75 g 2-h oral glucose tolerance test. The study group consisted of 370 participants with glucose intolerance at baseline.

Results: The conversion rates to normal glucose tolerance from impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) were 16.2% (95% confidence interval (CI) 13.30, 19.10) and 10.9% (95% CI: 5.7, 16.1) per year after an average of 2 years, respectively. Lower baseline fasting plasma glucose (HR 1.02, 95% CI: 1.01, 1.04) and 2-h (HR 1.02, 95% CI: 1.01, 1.04) glucose predicted conversion to NGT, as did changes in body mass index (BMI), waist circumference (WC), and lipids.

Conclusions: This is the first estimate of conversion rate and predictors from IFG and IGT to NGT in FDRs of people with type 2 diabetes in Iran. Lower baseline fasting, 2-h plasma glucose and changes in BMI, WC, and lipids predicted reversal to NGT at 24 months follow-up.

Keywords: Conversion rate; First-degree relatives; Impaired fasting glucose; Impaired glucose tolerance; Predictors; Regression rate