Participant characteristics
| Characteristic | Anaemia | Normal haemoglobin | Polycythaemia |
| Subjects n | 366 | 2048 | 125 |
| Age years | 70±9 | 68±8 | 66±8 |
| Female | 151 (41) | 956 (47) | 24 (19) |
| African American | 131 (36) | 451 (22) | 20 (16) |
| Education | |||
| Eighth grade or less | 12 (3) | 40(2) | 2 (2) |
| High school, no diploma | 45 (12) | 177 (9) | 6 (5) |
| High school graduate or GED | 93 (25) | 505 (25) | 29 (23) |
| Some college, no degree | 113 (31) | 561 (27) | 43 (34) |
| College or technical degree | 75 (20) | 548 (27) | 32 (26) |
| Master's or Doctoral degree | 28 (8) | 217 (11) | 13 (10) |
| BMI kg·m−2 | 29±7 | 28±6 | 28±5 |
| Smoking status | |||
| Former smoker | 267 (73) | 1321 (65) | 55 (44) |
| Current smoker | 99 (27) | 727 (36) | 70 (56) |
| Smoking history pack-years | 53±26 | 50±25 | 50±21 |
| Oxygen use | 123 (37) | 453 (22) | 24 (19) |
| Resting oxygen saturation % | 95±4 | 95±3 | 94±4 |
| Congestive heart failure | 49 (13) | 87 (4) | 5 (4) |
| Coronary artery disease | 55(15) | 221 (11) | 17 (14) |
| Hypertension | 252 (69) | 1069 (52) | 68 (54) |
| Diabetes | 81 (22) | 326 (16) | 16 (13) |
| Chronic kidney disease | 34 (9) | 58 (3) | 1 (1) |
| Sleep apnoea | 38 (10) | 242 (12) | 15 (12) |
| FEV1% predicted | 57±22 | 61±23 | 59±20 |
| FVC % predicted | 79±20 | 83±20 | 80±18 |
| FEV1/FVC ratio | 0.53±0.13 | 0.54±0.12 | 0.55±0.12 |
| DLCO % predicted | 62±22 | 67±22 | 67±23 |
| %LAA−950, median (IQR) | 5 (2–16) | 6 (2–16) | 5 (2–12) |
| LAA−950 >5%# | 159 (51) | 994 (53) | 55 (48) |
| MCV fL | 89±8 | 92±5 | 94±4 |
Data are presented as mean±sd or n (%), unless otherwise stated. Study population of COPD participants, Global Initiative for Chronic Obstructive Lung Disease 1–4 with anaemia and polycythaemia groups defined by haemoglobin cut-off values. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; DLCO: diffusing capacity of the lung for carbon monoxide; GED: General Education Diploma; IQR: interquartile range: LAA−950: low attenuation area <−950 HU, representing emphysema; MCV: mean corpuscular volume. #: emphysema was available for n=2299.