Proximity to traffic, ambient air pollution, and community noise in relation to incident rheumatoid arthritis
De Roos, AJ; Koehoorn, M; Tamburic, L; Davies, HW; Brauer, M
BACKGROUND: Risk of rheumatoid arthritis (RA) has been associated with living near traffic, however there is evidence suggesting that air pollution is not responsible for this association. Noise, another traffic-generated exposure, has not been studied as a risk factor for RA.
OBJECTIVES: We investigated proximity to traffic, ambient air pollution, and community noise in relation to RA in the Vancouver and Victoria regions of British Columbia, Canada.
METHODS: Cases and controls were identified in a cohort of adults, assembled using health insurance registration records. Incident RA cases from 1999 through 2002 were identified by diagnostic codes in combination with prescriptions and type of physician (e.g., rheumatologist). Controls were matched to RA cases by age and sex. Environmental exposures were assigned to each member of the study population by their residential postal code(s). We estimated relative risks using conditional logistic regression, with additional adjustment for median income at the postal code.
RESULTS: RA incidence was increased with proximity to traffic, with an odds ratio (OR) of 1.37 (95% confidence interval [CI]: 1.11, 1.68) for residence within 50 m of a highway compared to residence > 150 m away. There was no association with traffic-related exposures such as PM2.5, NO/NO2, or noise. Ground-level ozone, highest in suburban areas, was associated with increased risk of RA (OR = 1.26; 95% CI: 1.18, 1.36 for interquartile range increase).
CONCLUSIONS: Our study confirms a previously observed association of RA risk with proximity to traffic, and suggests that neither noise levels nor traffic-related air pollutants are responsible for this relationship. Additional investigation of neighborhood and individual correlates of residence near roadways may provide new insight into risk factors for RA.