ArticleThe association between urban form and physical activity in U.S. adults
Introduction
Ecologic models of behavior suggest that factors at a variety of levels, from the individual to the community, influence the prevalence of health-related behaviors.1 The ecologic approach has been widely discussed in the context of physical activity behavior because of the obvious dependence of physical activity on both individual propensity to be active and environmental features that facilitate physical activity.2 Examples of such features include sidewalks or paths, safe and desirable destinations for walking and cycling, recreational facilities, and a suitable climate.
Health promotion initiatives have already adopted an ecologic model, particularly in the area of physical activity.3 For example, the Centers for Disease Control and Prevention4 has been promoting the “Active Community Environments Initiative” to enhance activity by modifying the physical environment, but more research is needed to refine our assumptions about ecologic models.3
There is an extensive literature in the transportation research community concerning environmental effects on walking, cycling, and motorized transport use. These studies conceptualize the environment as “urban form” and have focused on transportation systems, such as transit availability and street characteristics, and on land development patterns, such as density and land use mix.5, 6 Transportation systems and land development are thought to directly influence transportation choices and a number of studies have linked transportation systems and land-use patterns to choices among different transport modes, including walking.7, 8 In an analysis of data from the 1995 National Personal Transportation Survey, Ross and Dunning9 showed that the percentage of trips using bicycling or walking as the transport mode was 3.3% in the lowest-density block groups (0 to 99 housing units per square mile), compared to 14.9% in the highest-density block groups (≥3000 units per square mile).
In addition to transportation systems and general patterns of land development, the concept of urban form encompasses building design, building orientation toward the street and other buildings, and detailed aspects of the distribution of homes, workplaces, and other institutions, such as schools, stores, and restaurants.10, 11 The complex nature of urban form makes it difficult and costly to develop comprehensive measures of urban form that may be related to physical activity, and there are significant disagreements over how the existing measures are related to each other and to behavior.6, 8, 10, 11, 12, 13 Understanding associations between urban form and transportation choices influencing physical activity levels is important for public health because of the possibility that planning decisions could influence physical activity and therefore health.
Home age is a candidate measure of urban form that is worthy of exploration for several reasons. First, home age is associated with density, street design, and building characteristics. Neighborhoods containing older homes in urban areas are more likely to have sidewalks, have denser interconnected networks of streets, and often display a mix of business and residential uses.10, 11 Second, ecologic studies suggest that there may be an association between home age and walking behavior; people living in census tracts with higher-mean home ages walk more than those living in tracts with lower-mean home ages.14, 15 Lastly, some existing health, transportation, and housing surveys contain data on home age. In this paper, we test the hypothesis that urban form influences levels of physical activity with an analysis of the association between home age, a proxy measure of urban form, and walking behavior in U.S. adults.
Section snippets
Methods
We analyzed data from the Third National Health and Nutrition Examination Survey (NHANES III). This survey is a nationally representative sample of the U.S. population with a stratified multistage probability design and oversampling of African Americans and Mexican Americans.16 A total of 17,030 adults aged ≥20 years responded to the household adult and family survey questions. Our analyses included adults aged ≥20 years who responded to questions concerning all of the behavioral and
Results
The distributions of walking behavior and home age stratified by several demographic variables are summarized in Table 1. Logistic regression indicated that there was a moderate association between gender and walking frequency (p = 0.062) and strong associations between walking and the remaining variables (p < 0.0001). Men were slightly more likely to walk ≥20 times per month than women. Non-Hispanic whites were more likely than other race/ethnic groups to report some walking and older
Discussion
Past work on the relationship between urban form and physical activity has explored the effects of population density, site design, and building characteristics on transportation behavior. Many of these studies report that increased density and mixed-use development are associated with more walking and bicycling.5, 7, 8, 12, 15, 20, 21 However, there is still considerable debate over the consistency and interpretation of such associations.10, 11, 13, 22 In this article, we extend past work by
Acknowledgements
DB was supported by a Cancer Prevention Fellowship from the National Cancer Institute while working on this project and gratefully acknowledges the Cooper Institute and its sponsors for organizing the symposium in which this paper was first presented. We are grateful to R. Ballard-Barbash, S. Krebs-Smith, K. Dodd, L. Mâsse, A. King, K. Calfas, and A. Bauman for helpful comments on the manuscript. Further comments by three anonymous reviewers also improved the manuscript.
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