HbA1c Variability and Diabetic Retinopathy in Asian Type 2 Diabetes

Abstract

Purpose: To examine the association of hemoglobin A1c (HbA1c) variability with diabetic retinopathy (DR) in Asian subjects with type 2 diabetes.

Methods: A retrospective study was conducted using data from a tertiary eye hospital in Singapore. Data from 234 Chinese, Malay and Indian adults with type 2 diabetes and serial 3-monthly HbA1c (range of 3-6) values over a 2-year period was collected. Retinal photographs, taken from both eyes, were graded for the presence and severity of DR after this 2-year period. Two groups were compared: 127 cases with moderate or worse DR (ETDRS level >=43) and 107 controls with diabetes but no DR. Intrapersonal standard deviation (SD) of serially measured A1C was considered a measure of variability. The association of HBA1c variability with the presence of moderate DR was examined using unconditional logistic regression models adjusted for potential confounders.

Results: The mean (7.9% versus 7.6%, p<0.001) and SD (0.53 versus 0.50, p<0.001) of serial HbA1c was significantly higher among cases with moderate DR compared to those without DR. In multivariable regression models adjusted for age, gender, ethnicity, duration of diabetes, hypertension, hyperlipidemia, smoking, microalbuminuria and cardiovascular events, both intrapersonal mean and SD of serially measured HbA1c were independently associated with moderate DR, with an odds ratio (OR) 1.99 (95% CI 1.39, 2.84) per unit increase of serial mean and OR 3.25 (95% CI 1.67, 6.34) per unit increase of serial SD. In models including both, serial mean HbA1c remained associated with moderate DR (OR 2.02, 95% CI 1.31, 3.12) but the association with serial SD was no longer statistically significant (OR 1.49, 95% CI 0.72, 3.07)

Conclusions: In Asian patients with type 2 diabetes, both higher mean HbA1c levels and increased HbA1c variability was associated with moderate or worse DR; however, assessment of HbA1c variability did not provide additional information on DR beyond mean values .

Keywords: 499 diabetic retinopathy • 498 diabetes