title: Upper gastrointestinal bleeding due to peptic ulcer disease is not associated with air pollution: a case-crossover study.
abstract: BACKGROUND
  Recent studies have demonstrated an association between short-term elevations in air pollution and an increased risk of exacerbating gastrointestinal disease. The objective of the study was to evaluate if day-to-day increases in air pollution concentrations were positively associated with upper gastrointestinal bleeding (UGIB) secondary to peptic ulcer disease (PUD).
  
  
  METHODS
  A time-stratified case-crossover study design was used. Adults presenting to hospitals with their first UGIB secondary to PUD from 2004-2010 were identified using administrative databases from Calgary (n = 1374; discovery cohort) and Edmonton (n = 1159; replication cohort). Daily concentrations of ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, and particulate matter (PM10 and PM2.5) were estimated in these two cities. Conditional logistic regression models were employed, adjusting for temperature and humidity. Odds ratios (OR) with 95 % confidence intervals (CI) were expressed relative to an interquartile range increase in the concentration of each pollutant.
  
  
  RESULTS
  No statistically significant associations were observed for any of the individual pollutants based on same-day, or 1-day lag effects within the Calgary discovery cohort. When the air pollution exposures were assessed as 3-, 5-, and 7-day averages, some pollutants were inversely associated with UGIB in the discovery cohort; for example, 5-day averages of nitrogen dioxide (OR = 0.68; 95 % CI: 0.53-0.88), and particulate matter <2.5 μm (OR = 0.75; 95 % CI: 0.61-0.90). However, these findings could not be reproduced in the replication cohort.
  
  
  CONCLUSIONS
  Our findings suggest that short-term elevations in the level of ambient air pollutants does not increase the incidence of UGIB secondary to PUD.
authors.affiliation: Departments of Medicine and Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Room 6D56, Calgary, AB, T2N-4N1, Canada. squan15@gmail.com.
authors.forename: Samuel
authors.initials: S
authors.lastname: Quan
authors.affiliation: Departments of Medicine and Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Room 6D56, Calgary, AB, T2N-4N1, Canada. hong.yang550@gmail.com.
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.affiliation: Departments of Medicine and Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Room 6D56, Calgary, AB, T2N-4N1, Canada. dtanying@ucalgary.ca.
authors.forename: Divine
authors.initials: D
authors.lastname: Tanyingoh
authors.affiliation: Department of Health Sciences, Carleton University, Ottawa, Ottawa, K1S 5B6, Ontario, Canada. Paul.villeneuve@carleton.ca.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Villeneuve
authors.affiliation: Population Studies Division, Health Canada, Vancouver, British Columbia, V6C 1A1, Canada. Dave.Stieb@hc-sc.gc.ca.
authors.forename: David M
authors.initials: DM
authors.lastname: Stieb
authors.affiliation: Air Health Science Division, Health Canada, Ottawa, K1A 0K9, Ontario, Canada. markey.johnson@hc-sc.gc.ca.
authors.forename: Markey
authors.initials: M
authors.lastname: Johnson
authors.affiliation: Departments of Medicine and Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Room 6D56, Calgary, AB, T2N-4N1, Canada. rhilsden@ucalgary.ca.
authors.forename: Robert
authors.initials: R
authors.lastname: Hilsden
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, T6G-2R7, Alberta, Canada. karen.madsen@ualberta.ca.
authors.forename: Karen
authors.initials: K
authors.lastname: Madsen
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, T6G-2R7, Alberta, Canada. vanzanten@ualberta.ca.
authors.forename: Sander Veldhuyzen
authors.initials: SV
authors.lastname: van Zanten
authors.affiliation: Departments of Medicine and Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Room 6D56, Calgary, AB, T2N-4N1, Canada. knovak@ucalgary.ca.
authors.forename: Kerri
authors.initials: K
authors.lastname: Novak
authors.affiliation: Departments of Emergency Medicine, University of Calgary, Calgary, T2N-4N1, Alberta, Canada. Eddy.Lang@albertahealthservices.ca.
authors.forename: Eddy
authors.initials: E
authors.lastname: Lang
authors.affiliation: Departments of Medicine and Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Room 6D56, Calgary, AB, T2N-4N1, Canada. subrata.ghosh@albertahealthservices.ca.
authors.forename: Subrata
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Departments of Medicine and Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Room 6D56, Calgary, AB, T2N-4N1, Canada. ggkaplan@ucalgary.ca.
authors.forename: Gilaad G
authors.initials: GG
authors.lastname: Kaplan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000032:analysis* / Q000633:toxicity; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D000416:Alberta; D002248:Carbon Monoxide / Q000032:analysis / Q000633:toxicity; D016022:Case-Control Studies; D018592:Cross-Over Studies; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009589:Nitrogen Oxides / Q000032:analysis / Q000633:toxicity; D016017:Odds Ratio; D010126:Ozone / Q000032:analysis / Q000633:toxicity; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity; D010437:Peptic Ulcer / Q000139:chemically induced / Q000150:complications*; D010438:Peptic Ulcer Hemorrhage / Q000209:etiology*; D012307:Risk Factors; D013458:Sulfur Dioxide / Q000032:analysis / Q000633:toxicity; D041742:Upper Gastrointestinal Tract / Q000187:drug effects
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides; D052638:Particulate Matter; D013458:Sulfur Dioxide; D010126:Ozone; D002248:Carbon Monoxide