Abstract C87: Spatial accessibility to mammography services in the Lower Mississippi Delta states
Authors: Zahnd Whitney E. , McLafferty Sara , Sherman Recinda , Farner Susan , Klonoff-Cohen Hillary , Rosenblatt Karin 
Published: February 2019

Introduction: The Delta Regional Authority (DRA) is a federally designated region that includes 252 counties across 8 Lower Mississippi Delta Region states (Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee) and contains nearly 10 million residents. The DRA has a high proportion of African American residents, high levels of poverty, and is largely rural. As such, the region has limited access to health care services, which likely leads to underutilization of mammography services and the higher breast cancer mortality of the region compared to the non-DRA counties within these eight states. Limited spatial access to mammography has been shown, in some studies, to be associated with more advanced stage at diagnosis, which may contribute to greater mortality risk.

Objective: To assess spatial accessibility to mammography facilities in the DRA and non-DRA counties within the Lower Mississippi Delta Region states.

Methods: We obtained the locations of all mammography facilities within the Lower Mississippi Delta Region states from the Food and Drug Administration. We used data from the US Census Bureau's American Community Survey to estimate the number women of recommended screening age (i.e., 45-74, the available data most congruent with recommendations) in each census tract in these states. We implemented the enhanced two-step floating catchment area method to calculate census-tract level spatial accessibility scores (SAS). This method considers both supply of and demand for mammography services within a specified catchment area, such as 60-minute travel time, with weights applied to account for distance decay (i.e., people are less likely to access services that are further away). We calculated Global Moran's I and Local Moran's I to determine if these SAS were spatially clustered and where they were clustered, respectively, within the DRA. We also calculated univariate statistics to compare SAS in the DRA and non-DRA designations of the Lower Mississippi Delta Region states and by rural-urban status using the United States Department of Agriculture's Rural-Urban Commuting Area codes. Because SAS were skewed (i.e., not normally distributed), the nonparametric, Wilcoxon Sum Rank Test was used to compared scores.

Results: Global Moran's I indicated limited, but statistically significant, spatial autocorrelation within the DRA (Moran's I=0.17, Z-score=47.67, p&lt;0.001). Local Moran's I showed clusters of high SAS in the DRA designation of Illinois and the westernmost part of the Kentucky DRA designation. Low spatial access was clustered in much of the Arkansas DRA designation and parts of Tennessee and Mississippi (i.e., a cluster of low spatial access around Memphis). Smaller clusters of low spatial access were seen in southern Louisiana as well. There was no statistically significant difference in SAS by DRA designation, with median scores of 0.000175 and 0.000161 in the DRA and non-DRA designations, respectively (p=0.69). There were no differences in SAS scores stratified by state except for Illinois where median SAS were higher in the DRA compared to the non-DRA part of the state (0.000243 and 0.000156, respectively, p&lt;0.001). There were no differences in SAS between the rural and urban DRA and between the urban DRA and non-DRA. However, median spatial access was slightly higher in the rural DRA vs. the non-DRA (0.000171 vs. 0.000170, p=0.03).

Discussion: Despite disparities in mammography utilization and breast cancer mortality in the DRA, we found no differences in spatial access to mammography compared to the non-DRA designation of the 8 Lower Mississippi Delta states. However, we identified clusters of low spatial access to mammography in specific parts of the DRA. These areas may be appropriate areas to target with mobile mammography initiatives or construction of free-standing mammography facilities.

Citation Format: Whitney E. Zahnd, Sara McLafferty, Recinda Sherman, Susan Farner, Hillary Klonoff-Cohen, Karin Rosenblatt. Spatial accessibility to mammography services in the Lower Mississippi Delta states [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr C87.