Table 6– Description of subjects without chronic obstructive pulmonary disease (COPD) by chronic bronchitis#
VariablesWithout chronic bronchitisWith chronic bronchitisp-value
Subjects n4269284
Age yrs55.0±0.2255.4±0.710.5839
Female2684 (62.9)164 (57.8)0.0806
Body mass index kg·m−228.2±0.1028.9±0.440.1293
Smoking pack-yrs8.7±0.2914.4±1.24<0.0001
Smoking status
 Current1207 (28.3)103 (36.3)<0.0001
 Former1131 (26.5)89 (31.3)
 Never1928 (45.2)92 (32.4)
Self-reported diagnosis
 COPD113 (2.7)38 (13.4)<0.0001
 Asthma400 (9.4)78 (27.5)<0.0001
 Tuberculosis74 (1.7)14 (4.9)0.0002
 Lung cancer5 (0.1)0.5571
Exposures
 No occupational dust2223 (52.1)117 (41.2)0.0030
  <10 yrs1154 (27.0)102 (35.9)
  ≥10 yrs890 (20.9)65 (22.9)
 Any occupational dust exposure2044 (47.9)167 (58.8)0.0009
 Domestic coal1028 (24.1)100 (35.2)0.0001
 Domestic biomass2118 (49.6)152 (53.5)0.2141
 Domestic exposure to coal or biomass2435 (57.1)184 (64.8)0.0148
 Childhood pulmonary hospitalisation86 (2.0)13 (4.3)0.0054
Respiratory symptoms
 Wheeze823 (19.3)150 (52.8)<0.0001
 Dyspnoea1842 (43.6)187 (66.8)<0.0001
Any respiratory medication176 (4.1)51 (18.0)<0.0001
Any bronchodilator158 (3.7)47 (16.6)<0.0001
Chronic bronchodilator >3 months32 (0.8)10 (3.5)<0.0001
Any corticosteroid45 (1.1)15 (5.3)<0.0001
Chronic corticosteroid >3 months10 (0.2)5 (1.8)<0.0001
Comorbidity score1.0±0.021.4±0.07<0.0001
Short Form-12 physical score51.2±0.1447.3±0.60<0.0001
Limitation due to physical health720 (16.9)96 (33.8)<0.0001
Work limitation due to physical health680 (15.9)99 (34.9)<0.0001
Leisure impairment due to physical health361 (8.5)43 (15.1)0.0001
Pre-bronchodilator FEV1 % pred98.5±0.3195.5±1.140.0088
Post-bronchodilator FEV1 % pred101.7±0.3299.7±1.070.0608
Absolute FEV1 change mL82.2±2.8103.1±12.90.1096
Relative FEV1 change %3.71±0.204.97±1.020.2229
Pre-bronchodilator FVC % pred100.3±0.3198.5±1.030.0831
Post-bronchodilator FVC % pred99.4±0.3098.7±0.940.5434
Absolute FVC change mL-36.4±4.11-7.94±17.70.1150
Relative FVC change %-0.47±0.230.39±0.790.2944
Pre-bronchodilator FEV1/FVC77.5±0.1076.2±0.360.0005
Post-bronchodilator FEV1/FVC80.7±0.0879.5±0.300.0002
  • 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).