Table 2. Characteristics of patients with GOLD grade 1 COPD by cluster.
| Domain/Parameters | Cluster I (n = 18) | Cluster II (n = 45) | Cluster III (n = 22) | p-value | ||
|---|---|---|---|---|---|---|
| Cluster I versus II | Cluster I versus III | Cluster II versus III | ||||
| Demographics | ||||||
| Age, years | 64 ± 6 [61–66] | 61 ± 8 [58–64] | 66 ± 6 [63–69] | 0.46 | 0.58 | 0.03 |
| Male, n (%) | 9 (50) | 30 (67) | 14 (64) | 0.46 | ||
| BMI, kg•m–2 | 27 ± 3 [25–28] | 27 ± 4 [26–28] | 27 ± 4 [25–28] | 0.68 | 0.96 | 0.84 |
| Smoking status, former/active % | 94/6 | 60/40 | 59/41 | 0.02 | ||
| Smoking history, pack–years | 33 ± 15 [25–40] | 51 ± 22 [45–58] | 43 ± 15 [36–49] | 0.002 | 0.21 | 0.20 |
| Symptoms | ||||||
| Cough, no/yes % | 61/39 | 42/58 | 45/55 | 0.39 | ||
| BDI scale | 8.5 ± 1.9 [7.6–9.4] | 7.5 ± 2.1 [6.9–8.1] | 8.3 ± 1.0 [7.8–8.7] | 0.14 | 0.92 | 0.25 |
| Lung function | ||||||
| FEV1, L | 2.60 ± 0.67 [2.26–2.93] | 2.79 ± 0.69 [2.58–3.00] | 2.54 ± 0.62 [2.26–2.81] | 0.55 | 0.96 | 0.31 |
| FEV1, % predicted | 94 ± 12 [88–100] | 97 ± 13 [94–101] | 95 ± 10 [91–100] | 0.63 | 0.95 | 0.82 |
| FVC, L | 4.00 ± 0.98 [3.51–4.49] | 4.44 ± 1.14 [4.10–4.78] | 4.30 ± 0.99 [3.86–4.75] | 0.30 | 0.63 | 0.88 |
| FVC, % predicted | 118 ± 13 [111–124] | 124 ± 14 [119–128] | 130 ± 17 [122–137] | 0.32 | 0.02 | 0.22 |
| FEV1/FVC, % | 65 ± 5 [63–67] | 63 ± 5 [62–65] | 59 ± 6 [56–62] | 0.54 | 0.002 | 0.008 |
| FEV1/FVC, <LLN % | 61 | 76 | 86 | 0.18 | ||
| IC, L | 3.09 ± 0.91 [2.64–3.55] | 3.03 ± 1.02 [2.72–3.34] | 2.99 ± 0.80 [2.64–3.35] | 0.96 | 0.94 | 0.99 |
| IC, % predicted | 110 ± 20 [100–120] | 104 ± 21 [98–110] | 109 ± 19 [100–118] | 0.57 | 0.99 | 0.63 |
| TLC, L | 6.33 ± 1.16 [5.75–6.90] | 6.95 ± 1.62 [6.46–7.44] | 6.60 ± 1.22 [6.06–7.14] | 0.27 | 0.82 | 0.62 |
| TLC, % predicted | 107 ± 12 [101–113] | 113 ± 15 [109–118] | 111 ± 11 [106–116] | 0.20 | 0.52 | 0.86 |
| FRC, L | 3.25 ± 0.45 [3.03–3.48] | 3.92 ± 0.95 [3.64–4.22] | 3.64 ± 0.83 [3.28–4.02] | 0.01 | 0.32 | 0.40 |
| FRC, % predicted | 104 ± 16 [96–112] | 122 ± 25 [114–129] | 114 ± 23 [104–125] | 0.02 | 0.37 | 0.45 |
| RV, L | 2.24 ± 0.41 [2.05–2.45] | 2.71 ± 0.81 [2.47–2.95] | 2.48 ± 0.50 [2.26–2.70] | 0.04 | 0.53 | 0.38 |
| RV, % predicted | 102 ± 17 [93–110] | 123 ± 36 [112–134] | 110 ± 23 [100–120] | 0.03 | 0.68 | 0.21 |
| IC/TLC | 0.48 ± 0.07 [0.45–0.52] | 0.43 ± 0.08 [0.41–0.46] | 0.45 ± 0.09 [0.41–0.49] | 0.07 | 0.52 | 0.58 |
| RV/TLC | 0.36 ± 0.05 [0.33–0.39] | 0.39 ± 0.08 [0.37–0.42] | 0.38 ± 0.07 [0.35–0.42] | 0.27 | 0.64 | 0.84 |
| D lco, % predicted | 79 ± 15 [72–87] | 76 ± 23 [69–83] | 73 ± 18 [65–82] | 0.86 | 0.64 | 0.85 |
| Comorbidities | ||||||
| Hypertension, n (%) | 8 (44) | 16 (36) | 6 (27) | – | – | – |
| Dyslipidemia, n (%) | 7 (39) | 16 (36) | 7 (32) | – | – | – |
| Coronary heart disease, n (%) | 1 (6) | 5 (11) | 0 (0) | – | – | – |
| Diabetes, n (%) | 0 (0) | 2 (4) | 0 (0) | – | – | – |
| Neoplasia, n (%) | 2 (11) | 0 (0) | 0 (0) | – | – | – |
Data are mean ± SD [95% confidence interval], unless otherwise specified.
Reported p-values for the ordinal variables (distribution) refer to Chi-squared test values from the contingency analysis.
BMI: body mass index; BDI: baseline dyspnea index; FEV1: forced expiratory volume in 1 second; FVC: forced vital capacity; LLN: lower limit of normal; IC: inspiratory capacity; TLC: total lung capacity; FRC: functional residual capacity; RV: residual volume; D lco: diffusion capacity.