Short-term air pollution exposure and exacerbation events in mild to moderate COPD: a case-crossover study within the CanCOLD cohort

Thorax. 2023 Oct;78(10):974-982. doi: 10.1136/thorax-2022-219619. Epub 2023 May 5.

Abstract

Background: Infections are considered as leading causes of acute exacerbations of chronic obstructive pulmonary disease (COPD). Non-infectious risk factors such as short-term air pollution exposure may play a clinically important role. We sought to estimate the relationship between short-term air pollutant exposure and exacerbations in Canadian adults living with mild to moderate COPD.

Methods: In this case-crossover study, exacerbations ('symptom based': ≥48 hours of dyspnoea/sputum volume/purulence; 'event based': 'symptom based' plus requiring antibiotics/corticosteroids or healthcare use) were collected prospectively from 449 participants with spirometry-confirmed COPD within the Canadian Cohort Obstructive Lung Disease. Daily nitrogen dioxide (NO2), fine particulate matter (PM2.5), ground-level ozone (O3), composite of NO2 and O3 (Ox), mean temperature and relative humidity estimates were obtained from national databases. Time-stratified sampling of hazard and control periods on day '0' (day-of-event) and Lags ('-1' to '-6') were compared by fitting generalised estimating equation models. All data were dichotomised into 'warm' (May-October) and 'cool' (November-April) seasons. ORs and 95% CIs were estimated per IQR increase in pollutant concentrations.

Results: Increased warm season ambient concentration of NO2 was associated with symptom-based exacerbations on Lag-3 (1.14 (1.01 to 1.29), per IQR), and increased cool season ambient PM2.5 was associated with symptom-based exacerbations on Lag-1 (1.11 (1.03 to 1.20), per IQR). There was a negative association between warm season ambient O3 and symptom-based events on Lag-3 (0.73 (0.52 to 1.00), per IQR).

Conclusions: Short-term ambient NO2 and PM2.5 exposure were associated with increased odds of exacerbations in Canadians with mild to moderate COPD, further heightening the awareness of non-infectious triggers of COPD exacerbations.

Trial registration: ClinicalTrials.gov NCT00920348.

Keywords: COPD epidemiology; COPD exacerbations; COPD exacerbations mechanisms; Clinical epidemiology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Air Pollutants* / adverse effects
  • Air Pollutants* / analysis
  • Air Pollution* / adverse effects
  • Air Pollution* / analysis
  • Canada / epidemiology
  • Cross-Over Studies
  • Environmental Exposure / adverse effects
  • Environmental Exposure / analysis
  • Humans
  • Nitrogen Dioxide / adverse effects
  • Nitrogen Dioxide / analysis
  • Particulate Matter / adverse effects
  • Particulate Matter / analysis
  • Pulmonary Disease, Chronic Obstructive* / epidemiology
  • Pulmonary Disease, Chronic Obstructive* / etiology

Substances

  • Nitrogen Dioxide
  • Air Pollutants
  • Particulate Matter

Associated data

  • ClinicalTrials.gov/NCT00920348