Neighborhood Walkability and Change in Weight, Diabetes
Are walkable urban neighborhoods associated with a slower increase in overweight, obesity, and diabetes than less walkable ones?
This was a time-series analysis (2001 to 2012) using annual provincial health care (n ≈ 3 million per year) and biennial Canadian Community Health Survey (n ≈ 5,500 per cycle) data for adults (ages 30-64 years) living in Southern Ontario cities. Information on neighborhood walkability was derived from a validated index, with standardized scores ranging from 0 to 100. Higher scores indicated more walkability. Neighborhoods were ranked and classified into quintiles from lowest (quintile 1) to highest (quintile 5) walkability. The primary outcomes of interest were the annual prevalence of overweight, obesity, and diabetes incidence, adjusted for age, sex, area income, and ethnicity.
A total of 8,777 neighborhoods were included in this study. Compared with residents living in the least walkable neighborhoods, those in the most walkable areas were somewhat younger and more likely to be nonwhite or to have immigrated to Canada in the preceding 10 years. During the follow-up period, most neighborhoods remained in the same quintile (78% overall, 95% in quintile five) and 99% remained within one quintile of their baseline assignment (weighted κ for agreement = 0.85). In addition, the area population and residential density, street connectivity, and number of retail outlets and services in each quintile were fairly stable. The median walkability index was 16.8, ranging from 10.1 in quintile one to 35.2 in quintile five. Resident characteristics were generally similar across neighborhoods; however, poverty rates were higher in high- versus low-walkability areas. In 2001, the adjusted prevalence of overweight and obesity was lower in quintile five versus quintile one (43.3% vs. 53.5%; p < 0.001). Between 2001 and 2012, the prevalence increased in less walkable neighborhoods (absolute change, 5.4% [95% CI, 2.1%-8.8%] in quintile one, 6.7% [95% CI, 2.3%-11.1%] in quintile two, and 9.2% [95% CI, 6.2%-12.1%] in quintile three). The prevalence of overweight and obesity did not significantly change in areas of higher walkability (2.8% [95% CI, −1.4% to 7.0%] in quintile four and 2.1% [95% CI, −1.4% to 5.5%] in quintile five). In 2001, the adjusted diabetes incidence was lower in quintile five than other quintiles and declined by 2012 from 7.7 to 6.2 per 1,000 persons in quintile five (absolute change, −1.5 [95% CI, −2.6 to −0.4]) and 8.7 to 7.6 in quintile 4 (absolute change, −1.1 [95% CI, −2.2 to −0.05]).
In contrast, diabetes incidence did not change significantly in less walkable areas (change, −0.65 in quintile one [95% CI, −1.65 to 0.39], −0.5 in quintile 2 [95% CI, −1.5 to 0.5], and −0.9 in quintile three [95% CI, −1.9 to 0.02]). Rates of walking or cycling and public transit use were significantly higher than that of car use lower in quintile five versus quintile one at each time point, although daily walking and cycling frequencies increased only modestly from 2001 to 2011 in highly walkable areas. Leisure-time physical activity, diet, and smoking patterns did not vary by walkability (p > 0.05 for quintile one vs. quintile five for each outcome) and were relatively stable over time.
The investigators concluded that among adults residing in Ontario, Canada, higher neighborhood walkability was associated with decreased prevalence of overweight and obesity and decreased incidence of diabetes between 2001 and 2012. However, the ecologic nature of these findings and the lack of evidence that more walkable urban neighborhood design was associated with increased physical activity suggest that further research is necessary to assess whether the observed associations are causal.
These data suggest the importance of environmental factors in health. Whether changes in environmental factors including increasing walkability of neighborhoods would reduce overweight, obesity, and incident diabetes is an important question to be addressed.
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