Geographic Access Disparities to Clinical Trials in Diabetic Eye Disease in the United States

To identify geographic and socioeconomic variables predictive of residential proximity to diabetic eye disease clinical trial locations.Cross-sectional, retrospective study.De-identified census tract-level data from public datasets and trial-level data from ClinicalTrials.gov.Using public data from ClinicalTrials.gov, we identified all active interventional clinical trials in diabetic eye disease since 2017. After geolocating every trial site, we used an origin-destination cost-matrix to calculate the driving distance and travel time from the population-weighted United States census tract centroid to the nearest site. We then used public databases to identify census tract-level socioeconomic factors predictive of driving distance and time.Driving distance60 miles and time traveled60 minutes to the nearest clinical trial site.In a multivariate model, driving distance of more than 60 miles had a significant association with rural versus urban location (adjusted odds ratio, 5.22; 95% confidence interval [CI], 3.75-7.26; P0.001), percentage of population at less than 200% of federal poverty level compared with the fourth quartile (first quartile: adjusted odds ratio, 0.40 [95% CI, 0.29-0.55]; second quartile: adjusted odds ratio, 0.60 [95% CI, 0.47-0.77]; third quartile: adjusted odds ratio, 0.76 [95% CI, 0.63-0.91]; P 0.001) and the Midwest (adjusted odds ratio, 2.15; 95% CI, 1.13-4.07; P = 0.02), South (adjusted odds ratio, 2.71; 95% CI, 1.23-5.99; P = 0.01), and West (adjusted odds ratio, 3.01; 95% CI, 1.21-7.54; P = 0.02) regions as compared with the Northeast. Driving distance was associated with county-level prevalence of diabetes in the univariate model (odds ratio, 1.12; 95% CI, 1.06-1.19; P0.001), although it was nonsignificant in the multivariate model. Similar predictors were found for time traveled in minutes.Geographic maldistributions of clinical trial sites exist for diabetic eye disease in the United States. Those with higher travel burden are more likely to reside in a census tract that is rural, low income, and from areas outside the Northeast.