title: Combined effects of road traffic noise and ambient air pollution in relation to risk for stroke?
abstract: Exposure to road traffic noise and air pollution have both been associated with risk for stroke. The few studies including both exposures show inconsistent results. We aimed to investigate potential mutual confounding and combined effects between road traffic noise and air pollution in association with risk for stroke. In a population-based cohort of 57,053 people aged 50-64 years at enrollment, we identified 1999 incident stroke cases in national registries, followed by validation through medical records. Mean follow-up time was 11.2 years. Present and historical residential addresses from 1987 to 2009 were identified in national registers and road traffic noise and air pollution were modeled for all addresses. Analyses were done using Cox regression. A higher mean annual exposure at time of diagnosis of 10 µg/m(3) nitrogen dioxide (NO2) and 10 dB road traffic noise at the residential address was associated with ischemic stroke with incidence rate ratios (IRR) of 1.11 (95% CI: 1.03, 1.20) and 1.16 (95% CI: 1.07, 1.24), respectively, in single exposure models. In two-exposure models road traffic noise (IRR: 1.15) and not NO2 (IRR: 1.02) was associated with ischemic stroke. The strongest association was found for combination of high noise and high NO2 (IRR=1.28; 95% CI=1.09-1.52). Fatal stroke was positively associated with air pollution and not with traffic noise. In conclusion, in mutually adjusted models road traffic noise and not air pollution was associated ischemic stroke, while only air pollution affected risk for fatal strokes. There were indications of combined effects.
authors.affiliation: Diet, Genes and Environment, Danish Cancer Society Research Centre, Strandboulevarden 49, 2100 Copenhagen, Denmark. Electronic address: mettes@cancer.dk.
authors.forename: Mette
authors.initials: M
authors.lastname: Sørensen
authors.affiliation: Department of Neurology, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark.
authors.forename: Pernille
authors.initials: P
authors.lastname: Lühdorf
authors.affiliation: Department of Environmental Science, Aarhus University, Roskilde, Denmark.
authors.forename: Matthias
authors.initials: M
authors.lastname: Ketzel
authors.affiliation: Department of Public Health, Copenhagen University, Copenhagen, Denmark.
authors.forename: Zorana J
authors.initials: ZJ
authors.lastname: Andersen
authors.affiliation: Diet, Genes and Environment, Danish Cancer Society Research Centre, Strandboulevarden 49, 2100 Copenhagen, Denmark.
authors.forename: Anne
authors.initials: A
authors.lastname: Tjønneland
authors.affiliation: Department of Public Health, Section for Epidemiology, Aarhus University, Aarhus, Denmark; Department of Cardiology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Kim
authors.initials: K
authors.lastname: Overvad
authors.affiliation: Diet, Genes and Environment, Danish Cancer Society Research Centre, Strandboulevarden 49, 2100 Copenhagen, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Raaschou-Nielsen
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects; D000397:Air Pollution / Q000009:adverse effects*; D002545:Brain Ischemia / Q000453:epidemiology* / Q000209:etiology; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009585:Nitrogen Dioxide / Q000009:adverse effects*; D009622:Noise / Q000009:adverse effects*; D020521:Stroke / Q000209:etiology / Q000401:mortality*; D001335:Vehicle Emissions / Q000633:toxicity
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions; D009585:Nitrogen Dioxide
keywords: Air pollution; Cohort; Road traffic noise; Stroke