Although diabetes is a well-known risk factor for death, its impact on cancer death is not clearly understood. Furthermore, it remains controversial whether impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) are associated with increased risk of mortality. We investigated the impact of diabetes or glucose tolerance categories on all cause and cause-specific mortality.

Mortality analysis was conducted in three population-based cohort studies of 3,801 participants, divided according to fasting plasma glucose (FPG) (normal; stage 1 IFG [5.6≤FPG<6.1 mmol/L]; stage 2 IFG [6.1≤FPG<7.0 mmol/L]; diabetes mellitus [DM]-FPG); or 2-hour glucose after 75 g glucose loading (2hPG) (normal; IGT; DM-2hPG), or a combination of FPG and 2hPG criteria.

During a median follow-up of 11.0 years, 474 subjects died from all causes. Hazard ratios (HRs) for all cause death were higher in those with diabetes as defined by either FPG or 2hPG criteria than their normal counterparts (HR, 2.2, 95% confidence interval [CI], 1.6 to 2.9 for DM-FPG; HR, 2.0, 95% CI, 1.5 to 2.7 for DM-2hPG). Similarly, diabetes defined by either FPG or 2hPG was associated with cancer death (HR, 2.9, 95% CI, 1.7 to 5.0; and HR, 2.1, 95% CI, 1.2 to 3.9, respectively). Although neither IFG nor IGT conferred higher risk for death, when combining stage 2 IFG and/or IGT, the risk of all cause death was higher than in subjects with normal glucose regulation (HR, 1.3; 95% CI, 1.0 to 1.6).

Diabetes is associated with higher risk of death from all causes and cancer. In subjects without diabetes, stage 2 IFG and/or IGT confers increased risk for mortality.