Variability in hemoglobin A1c predicts all-cause mortality in patients with type 2 diabetes

BackgroundTo evaluate the relationship between hemoglobin A1c variability and all-cause mortality in type 2 diabetic patients.MethodsThis was a retrospective cohort study in type 2 diabetic patients followed for at least 2 years between 2003 and 2009. A1C variability was determined from the standard deviation or coefficient of variation of serial A1C values (A1C_SD or A1C_CV). Subjects were categorized into either the high or low A1C variability group according to their A1C_CV median. Hazard ratios (HRs) of various factors for all-cause mortality were determined from Cox's proportional hazard models.ResultsA total of 881 subjects (422 men, 459 women) were included and 73 (8.3%) died during follow-up. The follow-up period was 4.7 ± 2.3 years. All-cause mortality was higher in subjects with high A1C_CV (11.0% vs. 5.4%, p = 0.002). In the Kaplan–Meier failure curve, subjects with higher A1C_CV demonstrated a trend of higher mortality (p = 0.1). In multivariate Cox's proportional hazards models, A1C_SD and A1C_CV significantly predicted all-cause mortality with an HR of 1.987 (p = 0.02) and 1.062 (p = 0.013), respectively, after adjusting for age, gender, body mass index, duration of diabetes, mean systolic blood pressure, use of antihypertensives and statins, mean LDL-cholesterol, smoking status, chronic kidney disease, and mean A1C values (A1C_MEAN). The ability of A1C_SD and A1C_CV to predict all-cause mortality was more evident in subjects with relatively low A1C_MEAN.ConclusionsA1C variability is an important risk factor for all-cause mortality in type 2 diabetic patients.