Comparison of normal fasting and one-hour glucose levels as predictors of future diabetes during a 34-year follow-up

Introduction. Early identification of those at risk of developing type 2 diabetes (T2DM) is essential. We examined how normoglycemic levels of fasting blood glucose (FBG) and 1-hour glucose predict the development of diabetes among men initially at low risk. Methods. In the Helsinki Businessmen Study (men born in 1919-1934), 1,145 men had normal FBG (<5.0 mmol/L) in 1974, and 1-hour glucose values available. Multivariate, adjusted models were used to investigate how fasting and 1-hour glucose at baseline related to new-onset diabetes during a follow-up of 34 years. Results. The median FBG and 1-hour glucose values at baseline were 4.4 and 6.6 mmol/L, respectively. During follow-up, 108 men developed diabetes. The risk of incident diabetes was doubled for the highest quintile of FBG (fully adjusted relative risk (RR) 2.22, 95% confidence interval (CI) 1.10-4.50), and quadrupled for that of 1-hour glucose (RR 4.23, 95% CI 2.49-7.17). FBG could not separate the risk for those with higher levels of glucose in the range <5.0 mmol/L, whereas 1-hour glucose discriminated the risk better at higher values. Conclusions. Higher values in the normoglycemic range for both fasting and 1-hour glucose predicted long-term incidence of diabetes in healthy middle-aged men.