Table 1.
Baseline characteristics classified by arterial oxygen saturation (SpO 2 ) in 5,152 participants
| ≤92% | 93–95% | ≥96% | p-value | ||||
|---|---|---|---|---|---|---|---|
| n | (%) | n | (%) | n | (%) | ||
| All | 53 | (1.0) | 537 | (10.4) | 4,562 | (88.5) | |
| Sex | 0.47 | ||||||
| Female | 34 | (1.2) | 297 | (10.3) | 2,556 | (88.5) | |
| Male | 19 | (0.8) | 240 | (10.6) | 2,006 | (88.6) | |
| Age (years) | <0.001* | ||||||
| <60 | 1 | (0.1) | 57 | (5.3) | 1,027 | (94.7) | |
| 60–70 | 16 | (0.7) | 217 | (10.2) | 1,902 | (89.1) | |
| ≥70 | 36 | (1.9) | 263 | (13.6) | 1,633 | (84.5) | |
| Self-reported diseases | |||||||
| CVD | <0.001 | ||||||
| No | 39 | (0.9) | 410 | (9.6) | 3,814 | (89.5) | |
| Yes | 14 | (1.6) | 127 | (14.3) | 748 | (84.1) | |
| Asthma | <0.001 | ||||||
| No | 37 | (0.8) | 448 | (9.6) | 4,197 | (89.6) | |
| Yes | 16 | (3.4) | 89 | (18.9) | 365 | (77.7) | |
| COPD | <0.001 | ||||||
| No | 39 | (0.8) | 476 | (9.8) | 4,366 | (89.4) | |
| Yes | 14 | (5.2) | 61 | (22.5) | 196 | (72.3) | |
| Diabetes | 0.004 | ||||||
| No | 49 | (1.0) | 499 | (10.1) | 4,373 | (88.9) | |
| Yes | 4 | (1.7) | 38 | (16.5) | 189 | (81.8) | |
| Hypertension | 0.020 | ||||||
| No | 40 | (1.0) | 378 | (9.7) | 3,463 | (89.2) | |
| Yes | 13 | (1.0) | 159 | (12.5) | 1099 | (86.5) | |
| Smoking history | 0.001* | ||||||
| Never | 16 | (0.9) | 141 | (8.1) | 1,581 | (91.0) | |
| Former | 21 | (1.0) | 241 | (11.6) | 1,819 | (87.4) | |
| Current | 16 | (1.2) | 155 | (11.6) | 1,162 | (87.2) | |
| Self-reported symptoms | |||||||
| Dyspnoea# | <0.001* | ||||||
| 0 | 17 | (0.6) | 221 | (8.0) | 2,511 | (91.3) | |
| 1 | 17 | (0.8) | 244 | (11.9) | 1,785 | (87.2) | |
| ≥2 | 19 | (5.3) | 72 | (20.2) | 266 | (74.5) | |
| Chronic cough with sputum | <0.001 | ||||||
| No | 44 | (0.9) | 460 | (9.7) | 4,261 | (89.4) | |
| Yes | 9 | (2.3) | 77 | (19.9) | 301 | (77.8) | |
| BMI (kg/m2) | <0.001* | ||||||
| <18.5 | 1 | (2.0) | 6 | (12.2) | 42 | (85.7) | |
| 18.5-24.9 | 16 | (1.0) | 107 | (6.4) | 1,548 | (92.6) | |
| 25.0-29.9 | 21 | (0.9) | 239 | (10.2) | 2,082 | (88.9) | |
| ≥30.0 | 15 | (1.4) | 180 | (17.0) | 865 | (81.6) | |
| CRP (mg/L) | <0.001 | ||||||
| <5 | 36 | (0.8) | 421 | (9.7) | 3,871 | (89.4) | |
| ≥5 | 17 | (2.3) | 109 | (14.7) | 615 | (83.0) | |
| Haemoglobin§ | 0.29 | ||||||
| ≤upper limit | 48 | (1.0) | 469 | (10.3) | 4,052 | (88.7) | |
| >upper limit | 0 | (0.0) | 4 | (21.1) | 15 | (78.9) | |
| FEV1% predicted | <0.001* | ||||||
| <50 | 16 | (8.2) | 66 | (34.0) | 112 | (57.7) | |
| 50–80 | 22 | (1.3) | 223 | (13.3) | 1,427 | (85.3) | |
| ≥80 | 13 | (0.4) | 227 | (7.3) | 2,882 | (92.3) | |
| FEV1/FVC% | <0.001 | ||||||
| <0.7 | 26 | (2.4) | 185 | (16.8) | 890 | (80.8) | |
| ≥0.7 | 25 | (0.6) | 335 | (8.6) | 3,551 | (90.8) | |
*Chi-square trend.
#Dyspnoea: 0, no dyspnoea; 1, dyspnoea walking rapidly on level ground or up a moderate slope; ≥2, dyspnoea walking slowly on level ground, washing or dressing, or at rest.
§Upper limits: women, 16.0 g/dL; men, 17.0 g/dL.
Definitions of abbreviations: SpO2, arterial oxygen saturation as measured by pulse oximetry; CVD, cardiovascular disease; COPD, chronic obstructive pulmonary disease; BMI, body mass index; CRP, C-reactive protein; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity.