Air pollution and long-term risk of hospital admission due to chronic obstructive pulmonary disease exacerbations in Poland: a time-stratified, case-crossover study.

INTRODUCTION:Airborne pollutants may worsen the course of chronic obstructive pulmonary disease (COPD). Previous studies have shown that both particulate and gaseous pollutants increase airway inflammation, which may lead to an exacerbation of COPD. OBJECTIVES:The aim of the study was to investigate the association between exposure to airborne pollutants and the risk of COPD exacerbations in 3 the largest urban agglomerations in Poland: Warsaw, Kraków, and Tricity. PATIENTS AND METHODS:We used a case‑crossover approach to analyze data from the years 2011-2018. This time‑series study used distributed lag linear-nonlinear models to analyze the risk of hospital admission due to COPD exacerbations during 21 days following the exposure to particulate matter (PM), NO2, and SO2. RESULTS:Overall, there were 26 948 admissions due to COPD exacerbations. During 21 days after exposure, the rate ratio (95% CI) for admissions per 10 μg/m3 was 1.028 (1.008-1.049) for PM10, 1.030 (1.006-1.055) for PM2.5, 1.032 (0.988-1.078) for NO2, and 1.145 (1.038-1.262) for SO2. The risk for admission peaked at 10 days after the exposure to PM10 and PM2.5, whereas for NO2 and SO2 the risk was the greatest on the day of exposure. The proportion (95% CI) of hospitalizations attributable to air pollution was 9.08% (3.10%-15.08%) for PM10, 7.61% (1.27%-13.49%) for PM2.5, 9.77% (-3.63% to 21.48%) for NO2, and 7.70% (2.30%-12.84%) for SO2. CONCLUSIONS:PM2.5, PM10, NO2, and SO2 pollution was associated with an increased risk of COPD exacerbations that needed hospitalization. There were different risk patterns for particulate and gaseous pollutants. Improving air quality in Polish cities could reduce the burden of COPD.