Diabetic retinopathy: contemporary prevalence in a well-controlled population

OBJECTIVE: To measure the extent to which modern intensified risk factor control has lessened the duration-specific prevalence of diabetic retinopathy and, therefore, has decreased the risk of blindness in Americans with type 2 diabetes. RESEARCH DESIGN AND METHODS: Intensified control of blood glucose and blood pressure has prevented diabetic retinopathy in randomized controlled trials. There is as yet no confirmation that subsequent treatment intensification in the community has had the same result. We identified all 6993 members of a health maintenance organization, Kaiser Permanente Northwest (KPNW), who, in 1997-1998, had dilated retinal examinations and verifiable data of diagnosis of type 2 diabetes. We plotted prevalence by time since diagnosis for background diabetic retinopathy (BDR) and proliferative diabetic retinopathy (PDR) and compared these results to identically derived 1980-1982 results from the Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR). We estimated multivariate predictive models. RESULTS: Mean (+/- SD) HbA(1c) in KPNW was 7.84 +/- 1.26% versus 10.37% (standardized) in the WESDR. KPNW blood pressure averaged 138.6 +/- 13.8/79.5 +/- 7.4 mmHg compared with 147.0/79.0 in the WESDR. BDR was much less prevalent in KPNW, but PDR prevalence appeared unchanged. BDR preceded diagnosis in 20.8% of the WESDR subjects but only 2.0% of KPNW subjects. However, in both populations, the first cases of PDR appeared similarly, soon after diagnosis. CONCLUSIONS: Earlier diagnosis and more aggressive control of blood glucose and blood pressure decreased the duration-adjusted prevalence of background, but not of sight-threatening proliferative retinopathy. More population-based research is needed to replicate and explain this unexpected finding. Detecting and treating PDR should not be neglected on the assumption that risk-factor control has minimized its prevalence.