Prevalence of retinopathy in diabetic subjects from out-patient clinics in Lombardy (Italy), and associated risk factors. A multicentre epidemiologic study.

There is little information on the prevalence of diabetic complications in Italy. For this reason, a multicentre population-based study was carried out in 1983-1985 in 12 representative out-patient clinics for the treatment of diabetes in the Lombardy region. Out of a total population of 17,704 patients 1160 diabetic subjects were randomly selected within strata based on their duration of disease (less than or equal to 5; 6-10; 11-20; greater than 20 years). Eight hundred and thirty-eight responders were examined using standardised protocols. The estimated prevalences (adjusted for duration of disease) for the total population involved in the study were 29.7% and 7.6% for background and proliferative retinopathy respectively. The overall standardised rates were higher in insulin-dependent diabetes mellitus (IDDM) (53.6%) than in non-insulin-dependent diabetes mellitus (NIDDM) (34.7%) for both background (41.1%, 28.4% respectively) and proliferative (12.5%, 6.2% respectively) retinopathy, and increased with the duration of disease. The analysis of the relationship between diabetic retinopathy and the calculated risk factors did not show any association with hypertension or metabolic control, except for post-prandial blood glucose in subjects with durations 6-10 and greater than 20 years; an association with azotaemia was found in subjects with durations less than or equal to 5 and 11-20 years. Diabetic retinopathy appeared to be independently associated with the type of treatment and not with the type of diabetes, metabolic control, or hypertension.