Association of neighborhood walkability with change in overweight, obesity, and diabetes

Importance — Rates of obesity and diabetes have increased substantially in recent decades; however the potential role of the built environment in mitigating these trends is unclear.

Objective — To examine whether walkable urban neighborhoods are associated with a slower rise in overweight, obesity and diabetes than less walkable neighborhoods.

Design, Setting, and Participants — Time series analysis (2001-2012) using annual provincial healthcare (N~3 million per year) and biennial Canadian Community Health Survey (N~5,500 per cycle) data for adults (30-64 years) living in Southern Ontario cities.

Exposure — Neighborhood walkability derived from a validated index, with standardized scores ranging from 0 to 100, with higher scores indicating more walkability. Neighborhoods were ranked and classified into quintiles from lowest (Q1) to highest (Q5) walkability.

Main Outcomes and Measures — Annual prevalence of overweight/obesity and diabetes incidence, adjusted for age, sex, area income and ethnicity.

Results — Among the 8777 neighborhoods included in this study, the median walkability index was 16.8, ranging from 10.1 in Q1 to 35.2 in Q5. 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/obesity was lower in Q5 vs. Q1 (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% to 8.8], +6.7% [95% CI, 2.3% to 11.1%, p=0.003], and +9.2 [95% CI, 6.2% to 12.1%,] in Q1, Q2, and Q3, respectively) but did not significantly change in areas of higher walkability (+2.8 [95%CI, -1.4% to +7.0%] in Q4 and +2.1 [95% CI, -1.4% to +5.5%,] in Q5). In 2001, the adjusted diabetes incidence per 1000 persons was lower in Q5 than other quintiles and declined by 2012 from 7.7 to 6.2 in Q5 (change:-1.5 [95%CI,-2.6 to -0.4]) and 8.7 to 7.6 in Q4 (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[95%CI, -1.65 to +0.39] in Q1, -0.5 [95% CI, -1.5 to +0.5] in Q2 and -0.9 [95%CI, -1.9 to +0.02] in Q3). Rates of walking/cycling and public transit use were significantly higher and car use lower in Q5 versus Q1, 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 Q1 vs. Q5 for each outcome) and were relatively stable over time.

Conclusions — In Ontario, Canada, higher neighborhood walkability was associated with decreased prevalence of overweight/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 suggests that further research is necessary to assess whether the observed associations are causal.