Density, destinations or both? A comparison of measures of walkability in relation to transportation behaviors, obesity and diabetes in Toronto, Canada

Abstract

The design of suburban communities encourages car dependency and discourages walking, characteristics that have been implicated in the rise of obesity. Walkability measures have been developed to capture these features of urban built environments. Our objective was to examine the individual and combined associations of residential density and the presence of walkable destinations, two of the most commonly used and potentially modifiable components of walkability measures, with transportation, overweight, obesity, and diabetes. We examined associations between a previously published walkability measure and transportation behaviors and health outcomes in Toronto, Canada, a city of 2.6 million people in 2011. Data sources included the Canada census, a transportation survey, a national health survey and a validated administrative diabetes database. We depicted interactions between residential density and the availability of walkable destinations graphically and examined them statistically using general linear modeling. Individuals living in more walkable areas were more than twice as likely to walk, bicycle or use public transit and were significantly less likely to drive or own a vehicle compared with those living in less walkable areas. Individuals in less walkable areas were up to one-third more likely to be obese or to have diabetes. Residential density and the availability of walkable destinations were each significantly associated with transportation and health outcomes. The combination of high levels of both measures was associated with the highest levels of walking or bicycling (p<0.0001) and public transit use (p<0.0026) and the lowest levels of automobile trips (p<0.0001), and diabetes prevalence (p<0.0001). We conclude that both residential density and the availability of walkable destinations are good measures of urban walkability and can be recommended for use by policy-makers, planners and public health officials. In our setting, the combination of both factors provided additional explanatory power.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Spatial Concordance Between Residential Density and Availability of Walkable Destinations.

Data from: the 2006 Canada Census; DMTI Spatial Inc., 2009; the City of Toronto, 2009; and the Ministry of Education, 2009. Residential density was calculated as the number of residential dwellings per square kilometer in all census disseminations blocks (DB) intersecting an 800 m buffer of a given DB's residentially-weighted centroid. Availability of walkable destinations was calculated as the number of retail and service destinations, including public recreation centers and schools, within an 800 m buffer of a given DB's residentially-weighted centroid. A DB was labeled ‘high’ for residential density or availability of walkable destinations if its value for that attribute placed it within the highest 2 quintiles for that attribute; similarly a DB was labeled as ‘low’ if its value placed it within the lowest 2 quintiles for that attribute.

Figure 2. Transportation Behaviors and Health Outcomes by Residential Density and Availability of Walkable Destinations.

These figures depict the interaction between density and destinations in relation to transportation behaviours and related health outcomes. The average daily number of trips per person by walking or bicycling, public transit, and automobile were derived from the Transportation Tomorrow Survey (2006) for residents age 11 years and older. Proportion of the population aged 30 to 64 years that were overweight and obese was derived from 2003–2008 Canadian Community Health Survey data. Age-sex adjusted prevalence of diabetes mellitus among adults aged 30 to 64 years was derived from the Ontario Diabetes Database, 2009. Residential density was calculated using data from the 2006 Canada Census and availability of walkable destinations was calculated using data from DMTI Spatial Inc. (2009), the City of Toronto (2009), and the Ministry of Education (2009).