Association between HbA1c variability and mortality in patients with type 2 diabetes

AimsWe aimed to evaluate the association between HbA1c variability and mortality due to all causes, cancer, and non-cancer in patients with type 2 diabetes independently of mean HbA1c levels.MethodsWe enrolled 754 patients with type 2 diabetes who first visited our hospital between 1995 and 1996, had been followed for at least 2 years, and had undergone four or more HbA1c determinations. Patients were followed through June 2012. The standard deviation (SD) or coefficient of variation (CV) was used as a measure of HbA1c variability. Risk of death was evaluated by multivariate Cox proportional hazard models.ResultsThrough June 2012, 63 patients died. Hazard ratios (HRs) for all-cause mortality and non-cancer mortality including cardiovascular diseases (CVD) increased across tertiles of both HbA1cSD and HbA1cCV. HRs for cancer mortality did not increase across tertiles of either HbA1cSD or HbA1cCV. Using a stepwise regression method, both HbA1cSD and HbA1cCV predicted all-cause mortality, especially non-cancer mortality. In contrast, mean HbA1c predicted cancer mortality.ConclusionsHbA1c variability is a predictor of all-cause mortality, especially non-cancer mortality including CVD, in patients with type 2 diabetes, independent of mean HbA1c level. In contrast, mean HbA1c, but not HbA1c variability, might predict cancer mortality.