The appearance of retinopathy and progression to proliferative retinopathy: the WHO multinational study of vascular disease in diabetes

Aims/hypothesis. We aimed to estimate incidences of any retinopathy and pro liferative diabetic retinopathy (PDR) by direct ophthalmoscopy and relate t hem to baseline risk factors in re-examined diabetic survivors from 10 cent res of the WHO Multinational Study of Vascular Disease in Diabetes. Methods. After a mean follow-up of 8.4 years (11.7 years in Oklahoma), 2877 (71.6%) survivors were resubmitted to standardised direct ophthalmoscopy a s at baseline. The presence of any retinopathy and PDR were recorded at eac h centre and their incidence estimated in those without retinopathy and PDR at baseline. The independent associations of these incidences with baselin e risk factors are expressed as odds ratios derived from multiple logistic regression analyses, within individual centres (which included fasting plas ma glucose in 8 and triglyceride in 5) and in pooled data. Results. Of the 4662 original patients, 465 (10.4%) of those without and 77 (43.0%) of those with baseline PDR had died (p < 0.001). Any retinopathy w as newly reported at follow-up in 47.7% and PDR in 9.7% of those free of th em at baseline, with reported incidences varying substantially among centre s. Incident retinopathy appeared earlier in the known course of diabetes bu t incidence rates rose more slowly with duration in patients with Type IT ( non-insulin-dependent) diabetes mellitus than in those with Type I (insulin -dependent) diabetes mellitus. In pooled data and in some individual centre s, any retinopathy incidence gave significantly positive odds ratios with a ge, diabetes duration, systolic pressure, plasma cholesterol, BMI, insulin treatment and proteinuria, and with fasting plasma glucose in the centres w here it was measured. Positive odds ratios for PDR were similarly obtained for age, duration, insulin treatment, cholesterol, proteinuria and fasting glycaemia. Smoking status odds ratios were negative for both outcomes. Conclusion/interpretation. Incidence of ophthalmoscopically ascertained any retinopathy varied about twofold and of PDR about threefold among centres. Although, in part attributable to differences between observers, variation in incidence in all centres and in some cases within centres was associate d with a number of baseline risk factors. Such associations are not likely due to observer variation or selection biases and emerged despite the impre cision of clinical ophthalmoscopy. Improved detection and control of these risk factors should reduce the impact of diabetic retinopathy and its conse quences.