title: Physical Activity, Air Pollution, and the Risk of Asthma and Chronic Obstructive Pulmonary Disease.
abstract: BACKGROUND
  Physical activity enhances uptake of air pollutants in the lung, possibly augmenting their harmful effects on chronic lung disease during exercise.
  
  
  OBJECTIVE
  To examine whether benefits of physical activity with respect to the risk of asthma and chronic obstructive pulmonary disease (COPD) are moderated by exposure to high air pollution levels in an urban setting.
  
  
  METHODS
  A total of 53,113 subjects (50-65 yr) from the Danish Diet, Cancer, and Health cohort reported physical activity at recruitment (1993-1997) and were followed until 2013 in the National Patient Register for incident hospitalizations for asthma and COPD. Levels of nitrogen dioxide (NO2) were estimated at subject residences at the time of recruitment. We used Cox regression to associate physical activities and NO2(high/medium/low) with asthma and COPD, and then introduced an interaction term between each physical activity and NO2.
  
  
  RESULTS
  A total of 1,151 subjects were hospitalized for asthma and 3,225 for COPD during 16 years. We found inverse associations of participation in sports (hazard ratio [95% confidence interval]: 0.85 [0.75-0.96]) and cycling (0.85 [0.75-0.96]) with incident asthma, and of participation in sports (0.82 [0.77-0.89]), cycling (0.81 [0.76-0.87]), gardening (0.88 [0.81-0.94]), and walking (0.85 [0.75-0.95]) with incident COPD admissions. We found positive associations between NO2and incident asthma (1.23 [1.04-1.47]) and COPD (1.15 [1.03-1.27]) hospitalizations (comparing ≥21.0 μg/m3to <14.3 μg/m3). We found no interaction between associations of any physical activity and NO2on incident asthma or COPD hospitalizations.
  
  
  CONCLUSIONS
  Increased exposure to air pollution during exercise does not outweigh beneficial effects of physical activity on the risk of asthma and COPD.
authors.affiliation: 1 Center for Epidemiology and.
authors.forename: Jack E
authors.initials: JE
authors.lastname: Fisher
authors.affiliation: 2 Section of Environmental Health, Department of Public Health, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Steffen
authors.initials: S
authors.lastname: Loft
authors.affiliation: 3 Department of Respiratory Medicine, Hvidovre Hospital and University of Copenhagen, Hvidovre, Denmark.
authors.forename: Charlotte S
authors.initials: CS
authors.lastname: Ulrik
authors.affiliation: 4 Danish Cancer Research Center, Danish Cancer Society, Copenhagen, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Raaschou-Nielsen
authors.affiliation: 5 Department of Environmental Science, Aarhus University, Roskilde, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Hertel
authors.affiliation: 4 Danish Cancer Research Center, Danish Cancer Society, Copenhagen, Denmark.
authors.forename: Anne
authors.initials: A
authors.lastname: Tjønneland
authors.affiliation: 6 Department of Public Health, Section for Epidemiology, Aarhus University, Aarhus, Denmark.|7 Department of Cardiology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Kim
authors.initials: K
authors.lastname: Overvad
authors.affiliation: 8 Center for Research in Environmental Epidemiology, Barcelona, Spain.|9 Universitat Pompeu Fabra, Barcelona, Spain; and.|10 Centro de Investigacion Biomedica en Red Epidemiología y Salud Pública, Barcelona, Spain.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Nieuwenhuijsen
authors.affiliation: 1 Center for Epidemiology and.
authors.forename: Zorana J
authors.identifier: http://orcid.org/0000-0003-4138-9828
authors.initials: ZJ
authors.lastname: Andersen
keywords: air pollution; asthma; chronic obstructive pulmonary disease; morbidity; physical activity