If you’ve ever missed a doctor’s appointment because you couldn’t find a ride to the clinic, you understand the relationship between public transit and health outcomes. A large body of research has established that communities that lack easy access to public transit are less healthy, in the aggregate, than communities with extensive, affordable transit networks.
Various studies have shown that transit access can reduce rates of heart disease, diabetes, obesity, vascular diseases, and other conditions associated with limb loss. Based on that evidence, it’s logical to infer that transit access affects the rate of limb loss as well. But there was never any direct data to support that inference until recently.
A study published last December in BMJ Open Diabetes Research found a direct correlation between access to public transit and the rate of amputations caused by diabetic foot ulcers (DFUs). Conducted by researchers affiliated with Emory University, the research was confined to a single state (Georgia) and a single four-year period (2016-19), so the conclusions are highly contingent. But this is still a significant paper, because it represents the first rigorous look at the associations between transportation access and DFU-related limb loss in the United States.
The authors focused on Georgia because it has a high prevalence of diabetes, above-average rates of socioeconomic distress, and large racial and ethnic minority populations. All of these demographic markers correlate with high DFU incidence, high amputation rates, and heavy reliance on public transit. The authors hypothesized that “increased access to healthcare through public transportation measures at the zip code level is associated with a decrease in DFU-related amputation rates.”
During the four-year study period, Georgia logged 1.1 million DFU cases, 14,782 minor amputations (ie toes and partial feet), and 6,606 major amputations (limb loss at the ankle or higher). The researchers plotted all those incidents by zip code, then wove in data regarding the proximity of transit stops, proximity of primary healthcare facilities, prevalence of automobile ownership, per-capita public transit expenditures, and a handful of other markers.
After crunching all of those numbers, the authors reported several key findings. First, higher reliance on public transit is associated with higher amputation rates, particularly in low-income zip codes. However, the inverse effect was observed in affluent zip codes with high proportions of household car ownership, which suggests that when riders choose public transit as an option rather than a necessity, they may derive limb-preserving health benefits from the higher activity levels (such as walking to/from bus stops or train stations) involved in transit ridership.
The researchers also found that heavier investment in public transportation was associated with lower amputation rates. Here, too, the correlation was affected by socioeconomic factors: In the lowest-income zip codes, amputation rates were not affected by gross public transit expenditures. Finally, low-income zip codes that were located a great distance from the nearest transit stop showed increased risk of DFU-related limb loss.
“Transportation is clearly a significant barrier to care for chronic diseases, including DFU, particularly for low-income populations,” the authors conclude. “Potential solutions to this problem include NEMT [non-emergency medical transportation], telemedicine, and mobile care….Future studies could investigate the impact of transportation assistance in conjunction with telemedicine and/or mobile clinics for DFU care.”
The full study, titled “Spatial associations between measures of public transportation and diabetic foot ulcer outcomes in the state of Georgia,” is available online at BMJ Open Diabetes Research & Care.
