Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Methods in Neuroepidemiology Neuroepidemiology 2010;34:131–142 DOI: 10.1159/000274807 Estimation of Short-Term Effects of Air Pollution on Stroke Hospital Admissions in Southern Sweden Anna Oudin a Ulf Strömberg a Kristina Jakobsson a, b Emilie Stroh a, b Jonas Björk a, c a Division of Occupational and Environmental Medicine, Lund University, b Occupational and Environmental Medicine, and c Competence Centre for Clinical Research, Lund University Hospital, Lund, Sweden eling facilitates a detailed exposure assessment but may also be more prone to misclassification errors. The time se- ries and case crossover approaches yielded similar effect estimates. Copyright © 2010 S. Karger AG, Basel Introduction Short-term exposure to air pollution has been linked to an increased risk of stroke in previous studies. Online supplementary table 1 (for all online suppl. material, see www.karger.com/doi/10.1159/000274807) provides an overview of the literature on short-term associations between stroke and air pollution that we refer to in this paper. Results from both animal and human experimental studies as well as observational studies have suggested several plausible mechanistic pathways linking air pol- lution to cardiovascular disease [1], including systemic inflammatory responses, arrhythmias, enhanced coag- ulation/thrombosis, acute arterial vasoconstriction, oxidative stress, endothelial function, hemodynamic re- sponses and the chronic promotion of atherosclerosis [2, 3] . Although relying on monitoring sites often far from the vicinity of the study subjects, a short-term (acute) ef- Key Words Epidemiology  Epidemiological methods  Air pollution  Stroke  Stroke risk factors Abstract Background: Short-term exposure to high levels of air pol- lution can increase stroke risk. In this study we investigated the short-term effects of air pollution on hospital admis- sions for stroke in a setting where pollutant levels are rath- er low. We also addressed methodological issues in evaluat- ing the short-term effects of air pollution. Methods: Daily admissions of ischemic (n = 11,267) and hemorrhagic (n = 1,681) stroke were obtained from a Swedish quality register for stroke, Riks-Stroke. We used two types of exposure data: (1) daily measured background levels of ozone, tempera- ture and particles with a diameter !10 m (PM 10 ) and (2) modeled levels of a mixture of NO and NO 2 (NO x ) at the residential address of each individual. Results: We estimat- ed a 13% (95% confidence interval, 4–22%) increased risk for hospital admissions for ischemic stroke for levels of PM 10 above 30 g/m 3 compared to !15 g/m 3 , whereas temper- ature above 16 ° C decreased the risk. No consistent associa- tions were found for hemorrhagic stroke or for ischemic stroke and ozone or NO x . Conclusion: Particulate air pollu- tion and temperature seemed to be associated with isch- emic stroke hospital admissions. Individual exposure mod- Received: August 31, 2009 Accepted: November 10, 2009 Published online: January 13, 2010 Anna Oudin Department of Occupational and Environmental Medicine Lund University SE–221 85 Lund (Sweden) Tel. +46 46 173 172, Fax +46 46 173 669, E-Mail anna.oudin @ med.lu.se © 2010 S. Karger AG, Basel 0251–5350/10/0343–0131$26.00/0 Accessible online at: www.karger.com/ned Downloaded by: 54.160.113.211 - 4/13/2017 3:37:08 PM