Blood glucose concentrations and progression of diabetic retinopathy: The seven year results of the Oslo study

Abstract

Objective - To study insulin dependent diabetic patients for change in non-proliferative retinopathy and its relation to glycaemic control and to various clinical background data. Design - Prospective study with follow up for seven years. Setting - Outpatient departments of university hospitals. Main outcome measures - Glycated haemoglobin concentration; degree of retinopathy. Results - Retinopathy worsened by an overall increase in counts of microaneurysms and haemorrhages from 17 (SD 25) to 45 (58) (p=0·005). Intensified insulin treatment and home blood glucose monitoring improved concentrations of glycated haemoglobin (HbA1) from 11·2% (2·2%) at the start of the study to a mean of 9·5% (1·5%) over the seven years of the study (p<0·0001). A mean value for HbA1 >10% was associated with an increased risk of progression of retinopathy and a mean value <8·7% was associated with a diminished risk. Multiple regression analysis identified four independent variables as indicative of outcome of retinopathy after seven years: HbA1 value at baseline; the change in HbA1 from start to the mean level through the seven years; duration of diabetes; and retinopathy at start. Age, blood pressure, and urinary albumin excretion were not related to the presence or progression of retinopathy. Conclusion - Secondary intervention by long term lowering of glycated haemoglobin has a beneficial impact on non-proliferative retinopathy. A four factor regression model can determine patients at high risk of severe retinopathy.