Measuring inequities in transportation injuries in a Canadian commuter cohort: impacts of individual versus neighbourhood income.

BACKGROUND: Low income has been associated with a higher risk of transportation-related injury however, previous studies have largely relied on area-level income, due to the limited availability of individual-level data. METHODS: To examine the independent and combined roles of individual- and area-level income, this prospective cohort study followed ~ 6,557,000 Canadians from the Canadian Census Health and Environment Cohorts (2006, 2011, 2016), for pedestrian, bicycling, or motor vehicle hospitalizations. Income was measured (1) individually by the low-income cut-off and (2) at the area level using neighbourhood income quintiles. Poisson regression estimated the incidence rate ratios (IRR) and 95% confidence intervals (CI) for transportation-related hospitalizations. RESULTS: After adjusting for covariates, low-income individuals had higher risks of hospitalizations for pedestrian (IRR = 1.93, 95%CI (1.62, 2.29)), bicycling (IRR = 1.16, 95%CI (1.01, 1.34)) and motor vehicle injuries (IRR = 1.18, 95%CI (1.06, 1.31)). When both individual and neighbourhood income were assessed together we estimated, that those who lived in the lowest income neighbourhoods (compared to the highest) had a higher risk of pedestrian (IRR = 1.80, 95%CI (1.51, 2.14)) and motor vehicle injury (IRR = 1.33, 95%CI (1.22, 1.42)) but lower risk of bicycling injury (IRR = 0.73, 95%CI (0.65, 0.81)). CONCLUSIONS: The interaction between individual and neighbourhood income revealed an increased injury risk for low-income individuals in all neighbourhoods, with large inequities in pedestrian and motor vehicle injury risk persisting even in the highest-income neighbourhoods. These findings demonstrate individual income independently contributes to transportation injury risk, underscoring the importance of considering both individual- and area-level income.