Patient characteristics of the study population
| Total COPD group | GOLD I | GOLD II | GOLD III | GOLD IV | p-value# | |
| Subjects n | 562 | 194 | 232 | 103 | 33 | |
| Sociodemographic characteristics | ||||||
| Age years | 73.9±5.9 | 74.4±5.9¶ | 74.5± 6.2¶ | 71.9±5.0 | 72.9±5.8 | 0.001 |
| Male | 433 (77.0) | 143 (73.7)¶ | 172 (74.1)¶ | 89 (86.4) | 29 (87.9) | 0.022 |
| Education years | 6.6±5.1 | 7.2±4.0 | 6.1±3.9 | 6.0±3.9 | 7.8±14.3 | 0.056 |
| Spirometry | ||||||
| FEV1/FVC | 57.2±11.5 | 65.1±4.1¶,+,§ | 59.2±7.6¶,§ | 44.6±10.3§ | 36.5±10.8 | <0.001 |
| FEV1 % pred | 69.1±24.7 | 95.6±12.8¶,+,§ | 65.9±8.9¶,§ | 40.0±60.0§ | 25.7±2.9 | <0.001 |
| Smoking habits | ||||||
| Smokers | 97 (17.3) | 27 (13.9) | 42 (18.1) | 22 (21.4) | 6 (18.2) | 0.005 |
| Former smokers | 341 (60.7) | 112 (57.7) | 134 (57.8) | 72 (69.9) | 23 (69.7) | |
| Never-smokers | 124 (22.1) | 55 (28.4) | 56 (24.1) | 9 (8.7) | 4 (12.2) | |
| Pack-years | 45.8±33.8 | 34.8±25.9¶,+ | 50.1±35.9 | 52.7±1.8 | 50.4±35.7 | <0.001 |
| Clinical characteristics | ||||||
| BMI kg·m−2 | 25.8±3.9 | 26.1±3.5§ | 26.1±4.0§ | 25.2±4.5 | 24.3±3.3 | 0.023 |
| GDS points | 3.5±3.2 | 2.8±3.0¶,+,§ | 3.7±3.2 | 4.1±3.4 | 5.0±3.4 | <0.001 |
| GDS >5 points | 144 (25.6) | 34 (17.5)¶,+,§ | 63 (27.2) | 35 (34.0) | 12 (36.4) | 0.005 |
| Visual impairment | 51 (9.1) | 16 (8.2) | 28 (12.1) | 4 (3.9) | 3 (9.1) | 0.109 |
| Hearing impairment | 42 (7.5) | 12 (6.2) | 2 (9.5) | 8 (7.8) | 0 (0.0) | 0.212 |
| Disease-specific health status | ||||||
| SGRQ symptom score | 47.2±24.8 | 30.0± 21.9¶,+,§ | 43.6±23.0¶,§ | 61.9±19.6 | 62.4±20.1 | <0.001 |
| SGRQ activity score | 48.4±27.5 | 28.5±24.5¶,+,§ | 45.3±26.3¶,§ | 61.2±20.4 | 73.3±17.0 | <0.001 |
| SGRQ impact score | 26.3±22.4 | 13.4±16.8¶,+,§ | 21.7±19.8¶ | 37.0±19.5§ | 49.7±24.3 | <0.001 |
| SGRQ total score | 37.1±22.1 | 21.2±18.1¶,+,§ | 33.1±19.8¶,§ | 49.2±17.3 | 59.0±18.5 | <0.001 |
| Physical functioning | ||||||
| 6MWT m | 317.4±120.2 | 341.0±123.8§ | 322.0±111.1¶,§ | 280.2±124.1 | 255.6±100.6 | <0.001 |
| 6MWT % pred | 24.6±35.7 | 23.3±36.8 | 24.4±36.7 | 26.1±33.3 | 29.6± 30.4 | 0.797 |
| Barthel index | 93.1±9.1 | 94.7±8.9§ | 93.1±9.3§ | 91.9±7.8 | 87.7±10.2 | <0.001 |
| Barthel index <80 | 40 (7.1) | 7 (3.6)§ | 16 (6.9)§ | 8 (7.8)§ | 9 (27.3) | <0.001 |
| Comorbid diseases | ||||||
| Myocardial infarction | 48 (8.5) | 66 (5.7)¶ | 31 (13.4)¶ | 4 (3.9) | 4 (12.1) | 0.003 |
| Congestive heart failure | 47 (8.4) | 10 (5.2)¶ | 30 (12.9)¶ | 3 (2.9) | 4 (12.1) | 0.004 |
| Peripheral vascular disease | 34 (6.0) | 14 (7.2) | 16 (6.9) | 4 (3.9) | 0 (0.0) | 0.292 |
| Cerebrovascular disease or ischaemic stroke | 22 (3.9) | 7 (3.6) | 11 (4.7) | 4 (3.9) | 0 (0.0) | 0.612 |
| Diabetes mellitus | 64 (11.4) | 18 (9.3) | 31 (13.4) | 9 (8.7) | 6 (18.2) | 0.264 |
| Solid or malignant tumours | 30 (5.3) | 10 (5.2) | 17 (7.3) | 2 (1.9) | 1 (3.0) | 0.210 |
| Parkinson's disease | 9 (1.6) | 3 (1.5) | 4 (1.7) | 2 (1.9) | 0 (0.0) | 0.888 |
Data are presented as n, mean±sd or n (%), unless otherwise stated. Missing variables were present for pack-years (24.2%) and St George's Respiratory Questionnaire (SGRQ) (34.5%). COPD: chronic obstructive pulmonary disease; GOLD: Global Initiative for Chronic Obstructive Lung Disease; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; BMI: body mass index; GDS: Geriatric Depression Scale; 6MWT: 6-min walk test. #: comparisons between patients with COPD in GOLD grades I–IV; ¶: p<0.05 versus GOLD III; +: p<0.05 versus GOLD II; §: p<0.05 versus GOLD IV.