Risk for future diabetes among individuals with high-normal glycemia at 40 years of age.

Objective: The present study investigated the risk for future diabetes among individuals with high-normal glycemia (fasting plasma glucose (FPG) of 100-109 mg/dL) in an early middle-aged population.

Methods: We retrospectively observed a workplace cohort all aged 40 and followed the incidence of diabetes according to the FPG levels at baseline. A total of 901 non-diabetic males were included in the analysis. The 10-year cumulative incidence of diabetes was calculated. The hazard ratios of developing diabetes were calculated using a Cox proportional hazards regression.

Results: The proportions of those with high-normal glycemia and impaired fasting glucose (IFG) (FPG of 110-125 mg/dL) at baseline were 21.5% and 4.7%. The 10-year cumulative incidence of diabetes was 14.7% and 48.9%, respectively, in these individuals. After adjustment for possible confounders, the hazard ratios of developing diabetes among individuals with high-normal glycemia and IFG were 5.2 (95% CI=2.4-11.2) and 21.3 (95% CI=9.2-49.5) relative to those with an FPG of <90 mg/dL.

Conclusion: High-normal glycemia is a risk for future diabetes even in the relatively young and healthy workplace population. Although the relative risk is much higher in those with IFG, the absolute number of incident diabetes developing from those with high-normal glycemia seems to be considerable given the prevalence of this condition.