Knowledge of subjects about the causes of COPD Subject Knowledge Total (5220) COPD1 Non COPD2 P (1&2) n% n% n% Smoking 2280 43.7 136 43.9 2144 43.7 > 0.05 EP1 1861 35.7 115 37.1 1746 35.6 > 0.05 OD2 787 15.1 41 13.2 746 15.2 > 0.05 Genetic factor 608 11.6 23 7.4 585 11.9 < 0.05 Unknown 2471 47.3 137 44.2 2334 47.5 > 0.05 (EP1: Environmental pollution; OD2: Occupation dust) Comments: 43.7% of subjects knew smoking was the cause of COPD.