Intrapersonal HbA(1c) variability and the risk of progression of nephropathy in patients with Type 2 diabetes.

Aim: To investigate the association between nephropathy and HbA(1c) variability (assessed as the standard deviation of each patient's HbA(1c) measurements) among patients with Type 2 diabetes.

Methods: Albumin excretion rate and HbA(1c) were measured in 2103 patients followed up for a mean 6.6 years. Multivariate Cox regression analysis was used to determine the influence of HbA(1c) variability on the risk of progression of nephropathy after adjustment for age, sex, duration of diabetes, baseline condition (two cohorts defined by duration of diabetes, retinopathy and albumin excretion rate), baseline HbA(1c) , insulin use, BMI, use of anti-hypertensive agents, smoking, lipid status, retinopathy, updated mean HbA(1c) and number of HbA(1c) measurements.

Results: Nephropathy progressed in 18.3% of subjects. HbA(1c) variability was significantly greater among progressors than among non-progressors (12 vs. 10 mmol/mol; 1.12 vs. 0.90%; P < 0.0001) and was a significant predictor of progression of nephropathy even after adjustment for updated mean HbA(1c) and other risk factors (hazard ratio 1.37, 95% CI 1.12-1.69).

Conclusion: In patients with Type 2 diabetes, the risk of progression of nephropathy increases significantly with HbA(1c) variability, independently of the influence of updated mean HbA(1c) .