Development of diabetic retinopathy and its associated risk factors in type 2 diabetic patients in Osaka district, Japan: a long-term prospective study.

Incidence rates of diabetic retinopathy and its associated risk factors were studied in a long-term prospective study involving 976 type 2 (non-insulin dependent) diabetic patients that showed no retinopathy at entry to the study. 322 of the patients (one-third of the subjects studied) developed diabetic retinopathy during the observation period (average length 8.3 years). The incidence rate per 1000 person-years was 39.8. The rate was significantly related to age at onset of diabetes, to fasting plasma glucose (FPG) level at entry, and to type of treatment. The incidence rate was also related to the duration of the disease. Glycemic control clearly played a role in the occurrence of retinopathy. Patients with FPG greater than or equal to 200 mg/dl had the highest incidence rate, while patients with FPG less than 140 mg/dl showed the lowest incidence rate throughout the observation period. Furthermore, a longer period between onset of diabetes and development of retinopathy was observed in patients with FPG less than 140 mg/dl compared to patients with FPG greater than or equal to 200 mg/dl. The findings suggest that strict glycemic control may be of particular value to reduce the incidence of retinopathy and to delay its appearance in type 2 diabetic patients.