Air Pollution and Ischemic Stroke Among Young Adults

Except that the conclusion doesn't necessarily follow if they haven't accounted for smokers. Don't they know about Occams' razor?
http://stroke.ahajournals.org/content/46/12/3348.abstract?

1. Maayan Yitshak Sade, MPH;
2. Victor Novack, MD, PhD;
3. Gal Ifergane, MD;
4. Anat Horev, MD;
5. Itai Kloog, PhD

+ Author Affiliations

1. From the Department of Medicine, Faculty of Health Sciences, Ben-Gurion University, Beer Sheva, Israel (M.Y.S., V.N.); Clinical Research Center (M.Y.S., V.N.) and Department of Neurology, Soroka University Medical Center, Beer Sheva, Israel (G.I., A.H.); and Department of Geography and Environmental Development, Faculty of Humanities and Social Sciences, Ben-Gurion University, Beer Sheva, Israel (I.K.).

1. Correspondence to Itai Kloog, PhD, Department of Geography and Environmental Development, Ben-Gurion University of the Negev, PO Box 653, Beer Sheva, Israel. E-mail ikloog@bgu.ac.il

Abstract

Background and Purpose—Studies have demonstrated consistent associations between cardiovascular illness and particulate matter (PM) <10 and <2.5 μm in diameter, but stroke received less attention. We hypothesized that air pollution, an inflammation progenitor, can be associated with stroke incidence in young patients in whom the usual risk factors for stroke are less prevalent. We aimed to evaluate the association between stroke incidence and exposure to PM <10 and <2.5 μm, in a desert area characterized by a wide range of PM.

Methods—We included all members of the largest health maintenance organization in Israel, who were admitted to a local hospital with stroke between 2005 and 2012. Exposure assessment was based on a hybrid model incorporating daily satellite remote sensing data at 1-km spatial resolution. We performed case-crossover analysis, stratified by personal characteristics and distance from main roads.

Results—We identified 4837 stroke cases (89.4% ischemic stroke). Interquartile range of PM <10 and <2.5 μm was 36.3 to 54.7 and 16.7 to 23.3 μg/m³, respectively. The subjects’ average age was 70 years; 53.4% were males. Associations between ischemic stroke and increases of interquartile range average concentrations of particulate matter <10 or <2.5 μm at the day of the event were observed among subjects <55 years (odds ratio [95% confidence interval], 1.11 [1.02–1.20] and 1.10 [1.00–1.21]). Stronger associations were observed in subjects living within 75 m from a main road (1.22 [1.03–1.43] and 1.26 [1.04–1.51]).

Conclusions—We observed higher risk for ischemic stroke associated with PM among young adults. This finding can be explained by the inflammatory mechanism, linking air pollution and stroke.