Table 5– Description of subjects with chronic obstructive pulmonary disease (COPD) by chronic bronchitis#
VariablesWithout chronic bronchitisWith chronic bronchitisp-value
Subjects n66396
Age yrs64.6±0.4760.6±1.160.0009
Female319 (48.1)43 (44.8)0.5276
Body mass index kg·m−226.8±0.1927.2±0.530.5244
Smoking pack-yrs17.9±0.9630.1±3.430.0006
Smoking status
 Current227(34.2)46 (47.9)0.0025
 Former216 (32.6)31 (32.3)0.0025
 Never220 (33.2)19 (19.8)
Self-reported diagnosis
 COPD60 (9.1)26 (27.1)<0.0001
 Asthma137 (20.7)36 (37.5)0.0003
Tuberculosis30 (4.5)9 (9.4)0.0494
Lung cancer6 (0.9)2 (2.1)0.2948
Respiratory symptoms
 Wheeze229 (34.5)66 (68.8)<0.0001
 Dyspnoea307 (47.0)72 (75.8)<0.0001
Exposures
 No occupational dust322 (48.6)34 (35.4)0.0344
  <10 yrs168 (25.3)32 (33.3)
  ≥10 yrs173 (26.1)30 (31.3)
 Any occupational dust exposure341 (51.4)62 (64.6)0.0249
 Domestic exposure to coal or biomass421 (63.5)68 (70.8)0.1666
 Childhood pulmonary hospitalisation16 (2.4)3 (3.1)0.6813
Any respiratory medication81 (12.2)32 (33.3)<0.0001
Any bronchodilator77 (11.6)30 (31.3)<0.0001
Chronic bronchodilator >3 months28 (4.2)23 (24.0)<0.0001
Any corticosteroid25 (3.8)17 (17.7)<0.0001
Chronic corticosteroid >3 months12 (1.8)11 (11.5)<0.0001
Comorbidity score1.1±0.041.4±0.110.575
Exacerbations in the past year2.1±0.955.3±3.830.4258
Short Form-12 physical score49.5±0.3644.6±1.01<0.0001
Limitation due to physical health148 (22.4)39 (40.6)0.0001
Work limitation due to physical health135 (20.4)38 (39.6)<0.0001
Leisure impairment due to physical health62 (9.4)19 (19.8)0.0029
Pre-bronchodilator FEV1 % pred81.0±0.9367.6±2.10<0.0001
Post-bronchodilator FEV1 % pred84.9±0.8573.0±2.10<0.0001
Absolute FEV1 change mL107.0±7.7135.5±17.60.1196
Relative FEV1 change %6.9±0.539.5±1.370.0654
Pre-bronchodilator FVC % pred99.6±0.9090.5±2.180.0001
Post-bronchodilator FVC % pred104.0±0.8296.0±2.320.0013
Absolute FVC change mL144.5±14.8160.4±41.20.7102
Relative FVC change %5.86±0.546.81±1.540.5487
Pre-bronchodilator FEV1/FVC62.1±0.3957.3±0.97<0.0001
Post-bronchodilator FEV1/FVC62.5±0.3258.6±1.020.0003
  • Data are presented as mean±se or n (%), unless otherwise stated. FEV1: forced expiratory volume in 1 s; % pred: % predicted; FVC: forced vital capacity. #: defined as phlegm on most days, at least 3 months per year for ≥2 yrs; : statistical tests for nominal variables: Pearson Chi-squared (adjusted for survey design); for ordinal variables: Mann-Whitney test; for continuous variables: Wald test (adjusted for survey design).