Mean HbA1c and HbA1c variability are associated with differing diabetes-related complications in patients with type 2 diabetes mellitus

Aims: To study the different effects of mean HbA1c and HbA1c variability on diabetes-related complications in patients with type 2 diabetes mellitus.Methods: 1869 patients with type 2 diabetes were followed-up for a median of 9.5 years in a Diabetes Shared Care Program. Mean HbA1c (HbA1c-mean) and standard deviation of HbA1c (HbA1c-SD) were calculated during the first 5 years. The clinical outcomes included nephropathy (urine albumin-to-creatinine ratio [UACR] > 300 mg/g and doubling of serum creatinine), retinopathy (any and advanced), and mortality (due to all-causes, and car-diovascular disease [CVD]).Results: HbA1c-mean was independently associated with UACR > 300 mg/g (Hazard ratio [HR] 1.308 [95% confidence interval {CI}, 1.194-1.433]), any retinopathy (HR 1.274 [1.171-1.385]), and advanced retinopathy (HR 1.237 [1.014-1.509]). HbA1c-SD was independently associated with UACR > 300 mg/g (HR 1.478 [1.189-1.837]), doubling of serum creatinine (HR 2.133 [1.470-3.095]), all-cause mortality (HR 1.880 [1.561-2.266]), and CVD mortality (HR 1.431 [1.069-1.915]). Receiver operating characteristic (ROC) curves showed HbA1c-mean was more associated with any retinopathy, whereas HbA1c-SD was more associated with doubling of serum creatinine, all-cause and CVD mortality.Conclusion: Both HbA1c-mean and HbA1c-SD predicted most diabetes-related complications in patients with type 2 diabetes. However, HbA1c-mean was more effective at predicting retinopathy, while HbA1c-SD was more effective at predicting deterioration of renal function and increased mortality.