Willingness to Pay Analysis of Elderly Diabetics for Confronting Diabetic Retinopathy

INTRODUCTION: Diabetic retinopathy (DR) is a frequent complication of diabetes mellitus (DM). The appearance of DR depends mainly on the duration of the diabetic disease and thus a diabetic who suffers from DM for 20 years, has a 90% probability to develop DR.  Aim: This study was conducted to measure how diabetic patients value risk reduction of DR, and estimate the maximum amount of money and percentage of monthly income these patients would pay for reduction of DR risk.METHODS: All patients gave written consent. 419 DM patients, aged ≥60 years were evaluated using «willingness to pay» (WTP) for cost-benefit analysis. After receiving background information, patients were asked how much money they would pay per month for a drug that would reduce their DR risk by 30%, 60% or 90%. Patients also indicated the importance of risk reduction on a 10-degree scale (0 = not important, 10 = extremely important). Data collected included demographic information, diabetes duration and treatment, presence of DR or symptoms, and whether patients knew someone with DM. Data normality was assessed with the Kolmogorov-Smirnov test. Differences between more groups (by education level, diabetes duration or monthly income) were evaluated with the Kruskal-Wallis test. The Mann-Whitney test was used to compare groups (men vs. women, knowing vs. not knowing someone with DM, having vs. not having DR) and for post-hoc comparisons. Factors influencing "WTP" were identified with logistic regression, using "WTP" > a certain income percentage as binary dependent variable. P values <0.05 were considered significant. RESULTS: Patients having DR were willing to pay more for risk reduction (p=0.002, p=0.007 and p=0.000 for reduction by 30, 60 or 90% respectively). Patients having DM for >10 years were willing to pay more (p=0.013, p=0.012 and p=0.002 for risk reduction by 30, 60 or 90% respectively). Diabetics using insulin were willing to pay more for risk reduction to 0% (p=0.002). Diabetics knowing other diabetics were also willing to pay more (p=0.032, p=0.017 and p=0.001 for risk reduction by 30, 60 or 90% respectively). Higher education and income were associated with willingness to pay more for risk reduction.CONCLUSIONS: DR risk reduction is important to DM patients, especially those having DM for >10 years, suffering from DR or knowing someone with DM. Education and monthly income significantly influence the perceived value of DR risk reduction.