The functional burden of diabetic retinopathy in the United States

Objective To study the association between diabetic retinopathy (DR) and physical functional difficulty using contemporary psychometric validation techniques, and to explore the predictors of physical difficulty among those with diabetes, non-proliferative DR (NPDR), or proliferative DR (PDR). Methods Cross-sectional study using the National Health and Nutrition Examination Survey (NHANES) database from 2005–2008. Participants were classified as either (i) no diabetes no DR, (ii) diabetes without DR, (iii) mild/moderate NPDR, or (iv) severe NPDR/PDR. The presence of DR was detected by retinal imaging and severity was graded using the Early Treatment Diabetic Retinopathy Study Protocol. The physical difficulty was assessed using a 13-question self-reported questionnaire, validated using factor analysis and item response theory (graded response model) psychometric techniques. Secondary analyses of diabetes and DR populations most at risk of reporting greater physical functional difficulty were undertaken. Results A total of 5321 participants over the age of 40 were included in our study. Of the 13 original physical difficulty questions, one latent trait was identified and 9 questions demonstrated good discrimination and were subsequently retained. In univariable analyses, participants with diabetes and any form of DR all reported significantly higher physical functional difficulty vs those with neither diabetes nor DR (p < 0.01 for all). In multivariable analyses, while those with diabetes or any form of DR remained more likely to report higher physical difficulty vs those with neither diabetes nor DR, only those with severe NPDR/PDR reported substantially higher scores (2.1 sum points higher, p = 0.002). Among participants with diabetes or any form of DR, those with 3 or more medical comorbidities and those with depression reported substantially higher sum physical difficulty scores ( p < 0.05 for all). Conclusions Those with diabetes or DR experience greater functional physical difficulty than those without, particularly profound among those with severe forms of DR. For those with DR, the presence of concurrent depression or medical comorbidities conferred a significantly higher risk of physical difficulty. Providers and healthcare systems should be aware of particularly vulnerable DR populations at increased risk of experiencing daily functioning deficits.