To identify and quantify risk factors for the development of long-term diabetic complications (i.e., critical limb ischemia, amputation, chronic renal failure [creatinine > 3 mg/dl], dialysis treatment, proliferative retinopathy, blindness), with particular emphasis on those variables that, being related to quality of care, can be considered avoidable.
We designed a case-control study that enrolled 886 patients with long-term diabetic complications and 1,888 control subjects without complications from 35 diabetic outpatient clinics and 49 general practitioners' offices during a 6-month period. Selected socioeconomic, pathophysiologic, self-care, health care, and lifestyle information were collected for all patients.
A logistic regression analysis showed that several factors are related to the development of major diabetic complications. Among patient characteristics, male sex (odds ratio [OR] = 1.8, 95% CI 1.4–2.3) and age (OR = 1.7, 95% CI 1.2–2.4 for patients between 50 and 69 years of age as opposed to those younger than 50 years of age) were associated with an increased risk of complication. Among clinical variables, the type and the duration of diabetes were the most important predictors of diabetic complications. The presence of hypertension was also associated with the development of diabetic complications, particularly when it was poorly controlled by treatment (OR = 3.1, 95% CI 2.3–4.3). Patients who needed help to reach a health care facility and those who did not regularly attend such a facility were at higher risk of developing complications (OR = 1.5, 95% CI 1.2–1.9; OR = 1.7, 95% CI 1.3–2.2, respectively). Educational aspects were also related to the outcome: patients who did not receive any kind of educational intervention had an increased risk of developing complications (OR = 4.1, 95% CI 1.7–9.7), while self-management of insulin therapy had a protective effect (OR = 0.6, 95% CI 0.5–0.8). The summary attributable risk related to avoidable risk factors (i.e., uncontrolled hypertension, poor compliance with visit scheduling, inadequate diabetes education, no self-management of insulin treatment) was 0.39.
Our data suggest that, by removing avoidable risk factors, the number of diabetic complications considered could be reduced by more than one-third. The case-control methodology represents an efficient way of monitoring clinical practice and relating it to important outcomes. It can be of help for policy makers in identifying the more effective strategies and in tailoring specific interventions aimed at improving the quality of the care delivered to diabetic patients.