Spatial associations between measures of public transportation and diabetic foot ulcer outcomes in the state of Georgia: 2016-2019

Introduction: There are limited data regarding the associations between public transportation reliance, availability, and diabetic foot ulcer (DFU)-related amputations.

Research design and methods: We used visit-level data from the Georgia 2016-2019 Healthcare Cost and Utilization Project database and obtained transportation variables from open sources. Using Bayesian spatial-temporal models, we assessed the associations between transportation and DFU-related amputations within each quartile of poverty status indicators at the ZIP code tabulation area (ZCTA) level. We used the proportion of adults who use public transportation to commute, distance to nearest transit stop, and per capita expense on public transportation as proxies for public transportation reliance, availability, and both, respectively.

Results: Of 114 606 DFUs, 21 388 (19%) were associated with a major or minor amputation. Among ZCTAs at the highest income quartile, reduced amputation risk was associated with the proportion of adults who use public transportation to commute to work (relative risk (RR)=0.29, 95% CI 0.09 to 0.97 per IQR increase of 1.13%) and per capita expense on public transportation (RR=0.78, 95% CI 0.63 to 0.78 per IQR increase of 6 cents). In metropolitan Georgia, a 1 IQR (261 m) increase in distance to the nearest transit stop was associated with lower amputation risk among ZCTAs at the lowest income quartile (RR=0.47, 95% CI 0.26 to 0.85).

Conclusion: In Georgia, public transportation reliance and availability are protective against DFU-related amputations in high-income but not among low-income ZCTAs. Reducing disparities in DFU-related amputations requires interventions to mitigate transportation barriers to care.