Interaction of walking activity and long-term air pollution on exacerbation rate in COPD

Background Regular walking activity can improve the prognosis in people with chronic obstructive pulmonary disease (COPD). However, its benefit may be reduced when living in highly polluted areas. Aim To assess the combined effects of walking activity and air pollution on the rate of moderate-to-severe exacerbation in COPD. Methods This prospective cohort study included 262 people with COPD from five European countries (United Kingdom, Spain, Belgium, Switzerland, Greece). Regular walking activity amount (walking bout step count, walking duration) and intensity (90thpercentile (P90) and average walking speed) was measured at baseline for seven days via single wearable devices. Residential concentrations of particulate matter<2.5 µm (PM 2.5 ), black carbon (BC), nitrogen dioxide (NO 2 ) and ozone (O 3 ) were estimated using land-use regression models for the previous two years. Moderate-to-severe exacerbations over a two-year follow-up were obtained from medical records and paper diaries. We estimated the interaction between walking activity and air pollution on long-term exacerbation rate with multivariable mixed-effects negative binomial models. Results Participants (32% female) were mean( sd ) 69(8) years old and had a forced expiratory volume in 1 s of 54(21)%-predicted. Higher step count and walking duration, but not P90 or average walking speed, were associated with a lower exacerbation rate (incidence rate ratio (95% confidence interval): 0.95 (0.91–0.99) per 1000 steps/day). No interaction was observed between step count, walking duration, or P90 or average walking speed and either PM 2.5 , BC, NO 2, or O 3 (p-for-interaction>0.2). Conclusion The benefits of regular walking activity in reducing COPD exacerbation rate are not modified by long-term Central- and Western-European air pollutant concentrations.