Background: To assess the incidence and progression of diabetic retinopathy and explore risk factors associated with them among non-insulin-dependent diabetes mellitus (NIDDM) patients.
Methods: A total of 471 NIDDM subjects aged > or 40 were recruited from four primary health care centres of northern Taiwan in 1986 and followed up for 4 years. Their ocular fundi were clearly visible by ophthalmoscopy and the status of diabetic retinopathy could be graded. A structured questionnaire interview was conducted to collect basic data. Overnight fasting venous blood was collected every year to measure the levels of glucose, glycosylated haemoglobin (HbA1c), cholesterol and high density lipoprotein cholesterol.
Results: Among the 344 subjects who had no retinopathy initially, 66 subjects developed retinopathy 4 years later giving a 4-year cumulative incidence of 19.2%. Of the 120 subjects initially with background or preproliferative retinopathy, evidence of deterioration developed in 36 subjects. The cumulative incidence of progression was 30%. Seven subjects developed proliferative retinopathy giving a cumulative incidence of progression to proliferative retinopathy of 5.8%. The univariate analysis disclosed that the development of retinopathy was correlated with mean fasting blood glucose (MFBG) and HbA1c, diabetic duration, diabetic treatment and residential area. The progression of retinopathy correlated with MFBG and proteinuria, and the progression to proliferative retinopathy correlated with MFBG. Stepwise logistic regression analysis revealed that MFBG and HbA1c were the significant risk factors related to the development of retinopathy.
Conclusions: Diabetic control assessed by MFBG or HbA1c was the significant risk factor correlated with the incidence and progression of retinopathy.