Traffic-Related Air Pollution Exposure and Incidence of Stroke in Four Cohorts from StockholmAbstract Number:2089 Michal Korek*, Tom Bellander, Matteo Bottai, Tomas Lind, Claes-Göran Östensson, Agneta Hilding, Ulf de Faire, Karin Leander, Laura Fratiglioni, Barbara Caracciolo, Nancy L Pedersen, Patrik Magnusson, Göran Pershagen, Johanna Penell Michal Korek* Institute of Environmental Medicine, Karolinska Institutet , Sweden, E-mail Address: [email protected] Search for more papers by this author , Tom Bellander Institute of Environmental medicine, Karolinska Institutet/ Centre for Occupational and Environmental Medicine, Stockholm County Council , Sweden, E-mail Address: [email protected] Search for more papers by this author , Matteo Bottai Institute of Environmental Medicine, Karolinska Institutet, Sweden, E-mail Address: [email protected] Search for more papers by this author , Tomas Lind Institute of Environmental medicine, Karolinska Institutet/ Centre for Occupational and Environmental Medicine, Stockholm County Council , Sweden, E-mail Address: [email protected] Search for more papers by this author , Claes-Göran Östensson Institute of environmental medicine, Department of Molecular Medicine and Surgery, Karolinska Institutet , Sweden, E-mail Address: [email protected] Search for more papers by this author , Agneta Hilding Institute of environmental medicine, Department of Molecular Medicine and Surgery, Karolinska Institutet , Sweden, E-mail Address: [email protected] Search for more papers by this author , Ulf de Faire Institute of Environmental Medicine, Karolinska Institutet , Sweden, E-mail Address: [email protected] Search for more papers by this author , Karin Leander Institute of Environmental Medicine, Karolinska Institutet, Sweden, E-mail Address: [email protected] Search for more papers by this author , Laura Fratiglioni Department of Neurobiology, Care Sciences and Society , Aging research Center, Karolinska Institutet , Sweden, E-mail Address: [email protected] Search for more papers by this author , Barbara Caracciolo Department of Neurobiology, Care Sciences and Society , Aging research Center, Karolinska Institutet , Sweden, E-mail Address: [email protected] Search for more papers by this author , Nancy L Pedersen Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Sweden, E-mail Address: [email protected] Search for more papers by this author , Patrik Magnusson Department of Medical Epidemiology and Biostatistics, Karolinska Institutet , Sweden, E-mail Address: [email protected] Search for more papers by this author , Göran Pershagen Institute of Environmental Medicine, Karolinska Institutet, Sweden, E-mail Address: [email protected] Search for more papers by this author , and Johanna Penell Department of Medical Sciences, Occupational and Environmental Medicine,Uppsala University , Sweden, E-mail Address: [email protected] Search for more papers by this author AbstractBackground Few studies have investigated the risk of stroke related to long-term ambient air pollution exposure, in particular the role of various exposure time-windows. We studied this in four cohorts in Stockholm County with a full residential history during up to 20 years.Methods The four cohorts included in total 22,587 individuals aged 35-104 years who were recruited between 1992 and 2004 and followed up until 2011. Air pollution exposure from local road traffic was assessed at each participant’s residence based on dispersion models for outdoor levels of particulate matter <10 µm in diameter (PM10) and nitrogen oxides (NOx). Cohort-specific Cox proportional hazard regression analyses assessed the relation between separate air pollution components and the incidence of stroke adjusting for common risk factors and results were combined by meta-analysis. The association with the risk of stroke was investigated for the exposure at recruitment into the cohort, and for the following exposure time-windows: 6-10, 4-6, 2-4 and 0-2 years prior to the end of each 6-months follow-up period.Results In total 868 subjects suffered a stroke during the 238,731 person-years of follow up. A difference of 20 µg/m³ estimated annual mean of road-traffic related NOx exposure at recruitment was associated with a hazard ratio of 1.16 ( 95% confidence interval 0.83- 1.61) with evidence of heterogeneity between cohorts. The result for road-traffic PM10 exposure was similar. Time-window analyses did not reveal any clear induction-latency pattern. However, this analysis was hampered by low power due to correlated exposures.Conclusions We found suggestive evidence of an association between exposure to NOx and PM10 from road traffic, and the risk of stroke. Observed heterogeneity between cohorts under study may have to do with differing exposure ranges, age distribution, study specific inclusion criteria and length of follow-up.