Higher neighbourhood drivability is associated with a higher diabetes risk in younger adults: a population-based cohort study in Toronto, Canada

Objective: Car dependency contributes to physical inactivity and consequently may increase the likelihood of diabetes. We investigated whether neighbourhoods that are highly conducive to driving confer a greater risk of developing diabetes, and if so whether this differs by age.

Research Design and Methods: We used administrative healthcare data to identify all working-aged Canadian adults (20-64 years) who were living in Toronto on April 1st 2011 without diabetes (type 1 or 2). Neighbourhood drivability scores were assigned using a novel, validated index that predicts driving patterns based on built environment features, divided into quintiles (Q). Cox regression was used to examine the association between neighbourhood drivability and 7-year risk of diabetes onset, overall and by age group, adjusting for baseline characteristics and comorbidities.

Results: Overall, there were 1,473,994 adults in the cohort (mean age 40.9±12.2), among whom 77,835 developed diabetes during follow-up. Those living in the most drivable neighbourhoods (Q5) had a 41% higher risk of developing diabetes compared to those in the least drivable neighbourhoods (adjusted HR: 1.41, 95%CI 1.37–1.44), with strongest associations in younger adults aged 20-34 years (1.57, 95%CI 1.47–1.68, p<0.001 for interaction). The same comparison in older adults (55-64 years) yielded smaller differences (1.31, 95%CI 1.26–1.36). Associations appeared to be strongest in middle-income neighbourhoods, for younger residents (middle income: 1.96, 95%CI 1.64-2.33) and older residents (1.46, 95%CI 1.32–1.62).

Conclusions: High neighbourhood drivability was a risk factor for diabetes, particularly in younger adults. This has important implications for future urban design policies.