Clinical characteristics of four groups
| Characteristics | LN/NA | HN/NA | LN/AT | HN/AT | P value |
| N | 141 | 90 | 146 | 205 | |
| Age (years) | 63.0±6.7 | 62.1±7.5 | 64.5±6.5 | 67.3±6.3*†‡ | <0.001 |
| Sex (male %) | 128 (90.8) | 81 (96.6)‡ | 141 (96.6)‡ | 199 (97.1)‡ | 0.013 |
| BMI | 23.6±3.1 | 23.4±3.1 | 21.8±3.2†‡ | 21.0±3.1†‡ | <0.001 |
| Smoking status (%) |
| <0.001 | |||
| Never smoked | 18 (12.8) | 17 (18.9) | 9 (6.2)† | 14 (6.8)† | |
| Former smoking | 25 (17.7) | 20 (22.2) | 48 (32.9)‡ | 75 (36.6)‡ | |
| Current smoking | 98 (69.5) | 53 (58.9) | 89 (61.0) | 116 (61.2) | |
| Smoking index (pack-year) | 41.4±34.7 | 33.8±30.8 | 40.9±32.6 | 39.9±30.9 | 0.308 |
| GOLD stage (%)** | <0.001 | ||||
| Stage I/II/III/IV | 61.0/39.0/0/0 | 63.4/33.3/3.3/0 | 26.0/57.5/12.3/4.1 | 24.4/51.7/11.5/1.5 | |
| Respiratory symptoms | |||||
| Chronic cough (n, %) | 49 (34.8) | 34 (37.8) | 69 (47.3) | 112 (54.6)‡ | <0.001 |
| Chronic sputum | 69 (48.9) | 44 (48.9) | 85 (58.2) | 130 (63.4)†‡ | 0.023 |
| Dyspnoea | 43 (30.5) | 32 (35.6) | 79 (54.1)†‡ | 115 (42.8)†‡ | <0.001 |
| CAT scores≥10 | 9 (6.4) | 12 (13.3) | 28 (19.2)‡ | 60 (29.3)†‡ | <0.001 |
| Exacerbation in the preceding year (%) | 7 (5.0) | 14 (15.6) | 33 (22.6)‡ | 38 (18.5)‡ | <0.001 |
| Previous respiratory disease | 7 (5.0) | 7 (7.8) | 17 (11.6) | 8 (3.9)* | 0.028 |
| Asthma | 5 (3.5) | 3 (3.3) | 5 (3.4) | 3 (18.8) | 0.579 |
| Tuberculosis | 2 (1.4) | 3 (3.3) | 10 (6.8)†‡ | 4 (2.0)* | 0.035 |
| Bronchiectasis | 0 (0.0) | 1 (1.1) | 2 (1.4) | 1 (0.5) | 0.507 |
| Inhaled medications | 5 (3.5) | 5 (5.6) | 14 (9.6) | 17 (8.3) | 0.181 |
| LAMA§ | 2 (1.4) | 2 (2.2) | 2 (1.4) | 6 (2.9) | 0.704 |
| LABA§ | 4 (2.8) | 2 (2.2) | 13 (8.9) | 11 (5.4) | 0.062 |
| ICS§ | 3 (2.1) | 2 (2.2) | 10 (6.8) | 10 (4.9) | 0.169 |
| pre-bronchodilator FEV1% predicted | 78.6±14.3 | 80.1±17.5 | 63.3±20.0†‡ | 60.6±19.8*†‡ | <0.001 |
| pre-bronchodilator FVC% predicted | 103.3±17.3 | 101.2±18.1 | 99.5±18.5 | 86.2±19.0*†‡ | <0.001 |
| pre-bronchodilator FEV1/FVC | 54.8±8.7 | 58.5±8.4‡ | 59.8±8.4‡ | 52.778±11.9*† | <0.001 |
| 1-year follow-up | N=119 | N=78 | N=133 | N=191 | |
| Exacerbation≥1/year (%) | 32 (26.9) | 22 (28.2) | 37 (27.8) | 74 (38.7) | 0.071 |
| Severe exacerbation (%) | 19 (16.0) | 18 (23.1) | 28 (21.1) | 61 (31.9)‡ | 0.010 |
| Exacerbation≥2/year (%) | 7 (5.9) | 10 (12.8) | 17 (12.8) | 29 (15.2) | 0.105 |
Data are presented by means±SD or number (percentages). Continuous variables were analysed by one-way analysis of variance with the Bonferroni method for multiple comparisons. Categorical variables were analysed by chi-square analysis with the Bonferroni method for multiple comparisons.
Bold indicates p<0.05.
*Compared with LN/AT group. P value less than 0.05.
†Compared with HN/NA group. P value less than 0.05.
‡Compared with LN/NA group. P value less than 0.05.
§Used alone or in combination.
**The Global Initiative for Chronic Obstructive Lung Disease (GOLD) staging system is used to assess the severity of lung disease. Stages range from I to IV. Stage I is defined as an FEV1 of 80% or more of the predicted value. Stage II is defined as an FEV1 between 50 and 79% of the predicted value. Stage III is defined as an FEV1 between 30 and 49% of the predicted value. Stage IV is defined as an FEV1 less than 30% of the predicted value.
BMI, body mass index; CAT, COPD Assessment Test; FEV1, forced expiratory volume in one second; FVC, forced vital capacity; HN/AT, high levels of sputum neutrophil proportion/air trapping; HN/NA, high levels of sputum neutrophil proportion/non-air trapping; ICS, inhaled corticosteroids; LABA, long-acting beta-agonists; LAMA, long-acting muscarinic antagonists; LN/AT, low levels of sputum neutrophil proportion/air trapping; LN/NA, low levels of sputum neutrophil proportion/non-air trapping.