Minimum Attainment Cost: National Benchmark Framework for Measuring Healthcare Accessibility in Alzheimer’s Disease and Related Dementias-Related Services

A threshold represented as travel time or distance is a key concept for determining catchment areas in cumulative opportunity and Two-Step Floating Catchment Area methods. As destinations included in a catchment area are determined by the threshold, it is a primary factor affecting spatial accessibility. In many cases, thresholds are arbitrarily determined or fixed values are used. The resulting accessibility based on these arbitrary or fixed thresholds makes it challenging to compare accessibility scores across heterogeneous geographic contexts (e.g., urban and rural areas). In this paper, we propose the Minimum Attainment Cost (MAC) as a context-sensitive spatial accessibility measure using the national average facility-to-population ratio as a benchmark and explore how fixed thresholds can over- or underestimate accessibility compared with MAC in a nationwide U.S. analysis. Using the national benchmark, MAC measures the minimum travel time required to reach the national average level of a given resource in each zone, accounting for the geographic distributions of demand and resources. By comparing MAC with multiple fixed thresholds (i.e., 30, 60, 90, and 120 minutes), we find that MAC is sensitive to geographic contexts in terms of the distributions of demand and resources. This approach enables direct geographic comparisons of spatial accessibility to different resources and provides evidence to support effective policy interventions by providing more context-sensitive accessibility estimates.