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Rate of β-Cell Destruction in Type 1 Diabetes Influences the Development of Diabetic Retinopathy: Protective Effect of Residual β-Cell Function for More Than 10 Years

Department of General Internal Medicine and Metabolism, Toranomon Hospital, Kawasaki 213-8587, Japan; and the Okinaka Memorial Institute for Medical Research, Tokyo 105-8470, Japan

Address all correspondence and requests for reprints to: Koji Nakanishi, Department of General Internal Medicine and Metabolism, Toranomon Hospital, 1-3-1 Kajigaya, Takatsu-ku, Kawasaki, Kanagawa 213-8587, Japan. E-mail: koji01{at}toranomon.gr.jp.

Context: Although residual β-cell function delays the onset and progression of diabetic retinopathy in patients with type 1 diabetes, the rate of β-cell destruction is variable.

Objective: The aim of the study was to clarify the influence of the rate of β-cell destruction on the development and progression of diabetic retinopathy in type 1 diabetes.

Design: We performed a historical cohort study regarding residual β-cell function and retinopathy.

Setting: The study was conducted in the outpatient clinic of a general hospital.

Patients: A total of 254 patients with type 1 diabetes participated.

Main Outcome Measures: Serum C-peptide and fundus findings were evaluated longitudinally.

Results: The cumulative incidence of mild nonproliferative diabetic retinopathy was higher in the patients without detectable β-cell function than in those with residual β-cell function at 20, 15, and 10 yr after the onset of diabetes (P = 0.013, P = 0.006, and P = 0.048, respectively), but not at 5 yr after the onset (P = 0.84). There were higher mean glycosylated hemoglobin values during the entire follow-up period in the patients without detectable β-cell function at 20 and 15 yr after the onset of diabetes (P = 0.030 and P = 0.042, respectively). Positivity for HLA-A24 and -DQA1*03, as well as the acute onset of diabetes, was associated with early β-cell loss and also with early development of diabetic retinopathy. Cox proportional hazards analysis showed that undetectable β-cell function at 20, 15, or 10 yr after the onset of diabetes was an independent risk factor for the development of diabetic retinopathy.

Conclusions: Undetectable β-cell function within 10 yr of the onset of type 1 diabetes is associated with the earlier occurrence of diabetic retinopathy.