Late Breaking Abstract - Estimating the relationship between environmental exposures and acute exacerbations of COPD

Abstract

<b>Background:</b> Chronic obstructive pulmonary disease (COPD) is a common and chronic lung condition characterized by sudden flare-ups known as acute exacerbations (AECOPD). Relative increases in air pollution concentration and ambient temperature may play a clinically relevant role in precipitating AECOPDs. <b>Objectives:</b> To estimate the association between short-term exposures to air pollution and exacerbations in patients with mild-moderate COPD, as well as the influence of temperature on this relationship. <b>Methods:</b> In this case-crossover study, AECOPD events were collected prospectively from COPD participants within the Canadian Cohort Obstructive Lung Disease (CanCOLD). Daily particulate matter &lt;2.5 microns (PM2.5), nitrogen dioxide (NO2), ozone (O3) and mean temperature estimates were obtained from national databases. Hazard and control periods on Day ‘0’ (day-of-event) as well as lags (Days ‘-1’ to ‘-6’) were compared by fitting conditional logistic regression models with generalized estimating equations. All data were dichotomized into ‘Warm’ (May-Oct.) and ‘Cool’ (Nov.-Apr.) periods. Single-pollutant models, unadjusted (un.) and adjusted (adj.) for mean temperature, were fitted. <b>Results:</b> Consistent positive associations (P&lt;0.05) were observed between NO2 (un. 1.11 [1.01,1.22], adj. 1.13 [1.02,1.26]) and PM2.5 (un. 1.11 [1.02,1.20], adj. 1.13 [1.03,1.24]) with AECOPDs on Lag Day -1 in the Cool period. The effects of O3 concentration on AECOPDs were equivocal. <b>Measurements and Main Results:</b> Exposure to ambient PM2.5 and NO2 was associated with an increased odds of AECOPD (particularly on lag Day -1 and during the Cool period), challenging the conventional understanding of the precipitants for AECOPD.