Aim: Diabetes mellitus (DM) outpatients were followed for 30 years or more. The impact of age and variability of fasting plasma glucose (FPG) and HbA(1C) on the onset of simple diabetic retinopathy (SDR) was analyzed.
Methods: The analysis included 84 DM patients who were free of retinopathy on their first visit between 1969 and 1977, then followed at the outpatients clinic through 2006. The plasma glucose and HbA(1C) were measured on every visit. The indices of variability were expressed as standard deviation (SD), coefficient of variance (CV) and range.
Results: The SDR incidence was significantly higher in the group of FPG SD > or =37 mg/dl (n=21) than in that of < 37 mg/dl (n=63). The hazard ratio, adjusted for the mean FPG, presence of hypoglycemia, age, duration of diabetes, hypertension and treatment of diabetes was 2.64 (95% CI: 1.26-5.50). The mean HbA(1C), HbA(1C) SD, mean FPG and FPG SD were significant risk factors for onset of SDR. Multivariate analysis identified the mean HbA(1C) and FPG SD as significant independent factors of increase in the risk of SDR onset. The SDR incidence was significantly lower in those aged 42 y or more (n=45) than in those under 42 y (n=39). The hazard ratio, adjusted for the mean FPG, gender, duration of diabetes, hypertension, and treatment of diabetes was 0.53 (95% CI: 0.30-0.95). All values for mean, SD and CV of FPG were significantly lower in the age group of > or = 42 y.
Conclusions: The risk of SDR onset in DM patients increased with the mean values of HbA(1C) and/or FPG and also with the variability of these parameters. The risk decreased in the group above age 42, which was speculated to be due to the smaller variability in FPG and also due to the fact that subjects included in the group started SDR at the age exceeded the age of predilection for SDR onset.