Neighborhood transportation vulnerability and geographic patterns of diabetes-related limb loss

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Transportation is paramount to health care access and minority populations face disproportionate transportation barriers in the United States (US). Health insurance coverage expansion has been the focus to achieve equitable health care in the US, but insurance alone does not guarantee access to care unless patients and providers can interact. Sixty percent of adults in the US have ≥1 chronic disease and current models of chronic disease care require frequent and ongoing contacts between patients and healthcare systems. Despite the advent of telehealth, most patient-provider interactions require patient transportation to a healthcare facility. US national-level surveys estimate 5.8 million people missed a health care appointment in 2017 due to transportation barriers and people of color face bigger transportation barriers to care. Our goal is to investigate the associations between “transportation vulnerability” and chronic disease outcomes at the neighborhood-level and to measure how race/ethnicity, sex, and age modify the magnitude of these associations using diabetic foot ulcers (DFUs) as a chronic disease model. “Transportation vulnerability” can arise from a combination of lacking transportation resources in an area, and from poor linkage between these resources and healthcare locations. Population-based studies linking transportation vulnerability to health outcomes are lacking. We choose DFU as model because they are a devastating diabetes complication preceding most of the 100,000 diabetes-related lower extremity amputations performed yearly in US. Low- income and racial minority groups experience higher burdens of DFUs and amputations. Importantly, the progression from ulceration to amputation is preventable with adequate outpatient care and DFUs have a clear poor outcome definition in the form of limb loss. Supported by a feasibility study, we will begin to fill this knowledge gap in this exploratory study by estimating the associations between transportation vulnerability and DFU outcomes using Georgia state-wide hospital billing databases, 2016-2020 (aim 1) and detailed patient- level records of two Atlanta-based large health systems, 2016-2021 (aim 2). This offers a unique opportunity to assess robustness of our findings from these two data sources with different advantages. Our research team has clinical expertise in DFUs, as well as chronic disease epidemiology, geographic information systems, and spatial epidemiology. This study is in line with the NIMHD research model by examining the intersection of the built environment and health care systems on health outcomes. Once in place, the framework developed will be extended to investigate the associations of transportation vulnerability and major diabetes complications (myocardial infarction, stroke, end-stage renal disease, and hyperglycemic crisis in addition to amputations) at a national-level. Our long-term goal is to develop a neighborhood-level US transportation vulnerability map to inform local interventions (e.g., allocation of non-emergency medical transportation services) and regional policies (e.g., development and improvement of public transit) to close disparities in healthcare access.