Residential proximity to high-traffic roadways and poststroke mortality

Background: Living in areas with higher levels of ambient air pollution has been associated with a higher incidence of ischemic stroke and all-cause mortality but less is known about the relationship between traffic-related pollution and long-term survival after stroke.

Methods: We identified consecutive patients admitted to Beth Israel Deaconess Medical Center with ischemic stroke between 1999 and 2008 and determined the distance to the nearest roadway with an average daily traffic count of more than 10,000 vehicles/day. Categories of residential proximity were defined as 100 m or less, 100-200 m, 200-400 m or less, or more than 400 m from a busy roadway. We identified deaths through June 2012 using the Social Security Death Index and used Cox proportional hazards models adjusted for medical history and socioeconomic factors to calculate hazard ratios for the association between residential proximity to a high-traffic roadway and all-cause mortality.

Results: Among 1683 stroke patients with complete data, there were 950 deaths (median follow-up=4.6 years). We observed higher poststroke mortality among people living closer to high-traffic roadways. Patients living 100 m or less from high-traffic roadways had a 20% (95% confidence interval: 1%, 43%) higher rate of poststroke mortality than patients living more than 400 m away (P trend=.02).

Conclusions: In this study, living close to a high-traffic roadway was associated with an elevated mortality rate. This relationship remained statistically significant after adjustment for individual- and neighborhood-level factors, providing evidence that traffic-related pollution is associated with a higher mortality rate among stroke survivors.