HbA1c variability and the development of microalbuminuria in type 2 diabetes: Tsukuba Kawai Diabetes Registry 2

Abstract

Aims/hypothesis: The aim of this study was to examine the association between HbA1c variability and the development of microalbuminuria as defined by an albumin/creatinine ratio ≥3.4 mg/mmol (≥30 mg/g) in at least two of three consecutive urine samples in Japanese patients with type 2 diabetes. Methods: HbA1c level was measured in 812 serially registered normoalbuminuric adults aged 21-79 years with type 2 diabetes. After registration, a 1-year period to establish baseline values for mean HbA 1c and HbA1c variability (measured as the intrapersonal SD of serially collected HbA1c) was decided upon. The association between HbA1c variability and the development of microalbuminuria was determined by Cox regression analysis after adjustment for other risk factors for microalbuminuria. Results: Microalbuminuria occurred in 193 patients during the observation period of (mean±SD) 4.3±2.7 years. Even after adjustment for mean HbA1c, HbA1c variability was a significant predictor of microalbuminuria independently of the mean HbA 1c; the HR for every 1% (95% CI) increase in mean HbA1c was 1.22 (1.06, 1.40) (p=0.005), and that for HbA1c variability was 1.35 (1.05, 1.72) (p=0.019). The effects of these two variables were quite similar when 1 SD was used; the HR for every 1 SD increase (95% CI) in HbA 1c was 1.23 (1.07, 1.43) (p=0.005), and that for HbA1c variability was 1.20 (1.03, 1.39) (p=0.019). Conclusions/interpretation: HbA1c variability affects the development of microalbuminuria independently of mean HbA1c in type 2 diabetes. Further studies should be performed to evaluate the influence of HbA1c variability on other complications and in individuals of other ethnicities with type 2 diabetes. © Springer-Verlag 2012.