Metrics of Urbanicity and Rurality in US-Based Epidemiologic Studies of Ambient Temperature and Health: A Scoping Review

Abstract

Background: The impacts of environmental health risk factors, including temperature, vary across urban and rural areas. Application of different metrics of rurality and urbanicity can yield different risk characterizations. We aimed to identify, describe, and quantify how urban/rural metrics are used in epidemiologic studies of ambient temperature and health across the United States (US). Methods: Using PubMed and Scopus, we identified epidemiologic studies published between January 2010 and March 2025 that examined ambient temperature and health in the US and included a defined, quantitative metric of urbanicity/rurality. Titles, abstracts, and full texts were evaluated by two independent reviewers. Data from included studies were extracted using a predetermined tool. Results: Of the 11,013 studies resulting from our search, 36 were included. We identified 23 metrics drawing from 10 data sources. The most frequently used metrics were population density and size from the US Census (n = 11 studies). Other metrics reflected connectivity and proximity to surrounding areas, such as the US Census’s Urban-Rural Classification (n = 7 studies), and the US Department of Agriculture’s Rural-Urban Commuting Area Codes (n = 4 studies) and Rural-Urban Continuum Codes (n = 2 studies). Additional metrics captured features related to the natural environment, built environment, and employment. Many studies did not provide a rationale for metric selection. Discussion: Urbanicity and rurality metrics have moved beyond population size and density to include other features. Providing rationales for choice of metric or the differential vulnerability or adaptive capacity captured by the metric could bolster understanding of urban-rural differences in the impact of temperature on health.