Travel Time to Radiation Oncology Facilities in the United States and the Influence of Certificate of Need Policies.

PURPOSE: Radiation therapy often requires weeks of daily treatment making travel distance a known barrier to care. However, the full extent and variability of travel burden, defined by travel time, across the nation is poorly understood. Additionally, some states restrict radiation oncology (RO) services through Certificate of Need (CON) policies, but it is unknown how this affects travel times to care. Therefore, we aim to evaluate travel times to US RO facilities and assess the association with CON policies. METHODS AND MATERIALS: RO facilities were identified from the 2018 National Plan and Provider Enumeration System (n = 2302). Travel times from populated US census tracts to nearest facility were calculated; differences by rurality, area deprivation, and region were computed. Multivariable linear regression was used to estimate adjusted differences in travel time by area characteristics. Logistic regression was used to assess the association of state CON laws with travel time >1 hour. RESULTS: Among 72,471 census tracts, 92.4% were within 1 hour of the nearest radiation facility. Among the 12,453 rural tracts, 34.4% were >1 hour. On adjusted analysis, the 3054 isolated rural tracts had an estimated 58-minute (95% confidence interval [CI] 57, 59; P < .001) longer travel time than urban tracts. CON laws decreased rural travel time overall, but the association varied by region with decreased odds of prolonged travel in the South (P < .001), increased odds in the Northeast and Midwest (P < .001), and no association in the West (P = NS). CONCLUSIONS: Isolated rural US census tracts, accounting for 9.4 million Americans, have nearly 1-hour longer adjusted travel time to the nearest RO facility, compared with urban tracts. CON laws had region-dependent associations with prolonged travel.

Climate Shocks and Migration: An Agent-Based Modeling Approach.

This is a study of migration responses to climate shocks. We construct an agent-based model that incorporates dynamic linkages between demographic behaviors, such as migration, marriage, and births, and agriculture and land use, which depend on rainfall patterns. The rules and parameterization of our model are empirically derived from qualitative and quantitative analyses of a well-studied demographic field site, Nang Rong district, Northeast Thailand. With this model, we simulate patterns of migration under four weather regimes in a rice economy: 1) a reference, 'normal' scenario; 2) seven years of unusually wet weather; 3) seven years of unusually dry weather; and 4) seven years of extremely variable weather. Results show relatively small impacts on migration. Experiments with the model show that existing high migration rates and strong selection factors, which are unaffected by climate change, are likely responsible for the weak migration response.

Changing crops in response to climate: virtual Nang Rong, Thailand in an agent based simulation.

The effects of extended climatic variability on agricultural land use were explored for the type of system found in villages of northeastern Thailand. An agent based model developed for the Nang Rong district was used to simulate land allotted to jasmine rice, heavy rice, cassava, and sugar cane. The land use choices in the model depended on likely economic outcomes, but included elements of bounded rationality in dependence on household demography. The socioeconomic dynamics are endogenous in the system, and climate changes were added as exogenous drivers. Villages changed their agricultural effort in many different ways. Most villages reduced the amount of land under cultivation, primarily with reduction in jasmine rice, but others did not. The variation in responses to climate change indicates potential sensitivity to initial conditions and path dependence for this type of system. The differences between our virtual villages and the real villages of the region indicate effects of bounded rationality and limits on model applications.

Design of an Agent-Based Model to Examine Population-Environment Interactions in Nang Rong District, Thailand.

The design of an Agent-Based Model (ABM) is described that integrates Social and Land Use Modules to examine population-environment interactions in a former agricultural frontier in Northeastern Thailand. The ABM is used to assess household income and wealth derived from agricultural production of lowland, rain-fed paddy rice and upland field crops in Nang Rong District as well as remittances returned to the household from family migrants who are engaged in off-farm employment in urban destinations. The ABM is supported by a longitudinal social survey of nearly 10,000 households, a deep satellite image time-series of land use change trajectories, multi-thematic social and ecological data organized within a GIS, and a suite of software modules that integrate data derived from an agricultural cropping system model (DSSAT - Decision Support for Agrotechnology Transfer) and a land suitability model (MAXENT - Maximum Entropy), in addition to multi-dimensional demographic survey data of individuals and households. The primary modules of the ABM are the Initialization Module, Migration Module, Assets Module, Land Suitability Module, Crop Yield Module, Fertilizer Module, and the Land Use Change Decision Module. The architecture of the ABM is described relative to module function and connectivity through uni-directional or bi-directional links. In general, the Social Modules simulate changes in human population and social networks, as well as changes in population migration and household assets, whereas the Land Use Modules simulate changes in land use types, land suitability, and crop yields. We emphasize the description of the Land Use Modules - the algorithms and interactions between the modules are described relative to the project goals of assessing household income and wealth relative to shifts in land use patterns, household demographics, population migration, social networks, and agricultural activities that collectively occur within a marginalized environment that is subjected to a suite of endogenous and exogenous dynamics.