Abbreviations
COPD, Chronic Obstructive Pulmonary Disease; CE, COPD exacerbation; HR, hazard ratio; PM10, Particulate matter less than 10 µm; SO2, Sulfur dioxide; NO2, Nitrogen dioxide; O3, ozone; WS, Wind speed; SS, Solar sunshine; KNHIS-NSC, Korea National Health Insurance Service-National Sample Cohort; DLNM, Distributed Lag Linear and Non-Linear Model; QAIC, quasi Akaike information criterion; PACF, partial autocorrelation function; DOW, Day of Week; RR, Risk ratio; CO, Carbon monoxide; DTR, diurnal temperature range; HM, humidity.