Summary statistics for baseline demographics and predictor variables
| Baseline variable | COPD in wave 9 | p-value | Overall | |
| No | Yes | |||
| Subjects n | 3475 | 109 | 3584 | |
| Age years | 47.6±1.5 | 47.7±1.4 | 0.205# | 47.6±1.5 |
| BMI kg·m−2 | 25.4±4.7 | 26.5±5.5 | 0.059# | 25.5±4.7 |
| SF-36 PCS | 51.9±7.8 | 49.9±9.3 | 0.035# | 51.9±7.9 |
| SF-36 MCS | 49.5±10.0 | 46.4±11.1 | 0.004# | 49.5±10.1 |
| SEIFA IRSD | 1011±86 | 1000±77 | 0.160# | 1010±85 |
| Education level | 0.009¶ | |||
| Less than high school | 1748 (42.8) | 61 (56.0) | 1539 (43.2) | |
| High school/trade/diploma | 1328 (38.5) | 33 (30.3) | 1361 (38.2) | |
| University/postgraduate | 645 (18.7) | 15 (13.8) | 660 (18.5) | |
| Presence of back pain | 0.077¶ | |||
| Never | 901 (26.0) | 20 (18.3) | 921 (25.8) | |
| Rarely | 932 (26.9) | 31 (28.4) | 963 (27.0) | |
| Sometimes | 1100 (31.8) | 37 (33.9) | 1137 (31.8) | |
| Often | 529 (15.3) | 21 (19.3) | 550 (15.4) | |
| Presence of chest pain | 0.204¶ | |||
| Never | 2769 (80.4) | 82 (75.2) | 2851 (80.2) | |
| Rarely | 419 (12.2) | 18 (16.5) | 437 (12.3) | |
| Sometimes/often | 256 (7.4) | 9 (8.3) | 265 (7.5) | |
| Breathing difficulties | <0.001¶ | |||
| Never | 2723 (78.9) | 62 (57.4) | 2785 (78.3) | |
| Rarely | 367 (10.6) | 23 (21.3) | 390 (11.0) | |
| Sometimes/often | 361 (10.5) | 23 (21.3) | 384 (10.8) | |
| Asthma | <0.001+ | |||
| No | 3104 (89.4) | 82 (75.2) | 3186 (89.0) | |
| Yes | 368 (10.6) | 27 (24.8) | 395 (11.0) | |
| Presence of allergies, hay fever, sinusitis | 0.002¶ | |||
| Never | 1478 (42.8) | 31 (28.7) | 1509 (42.4) | |
| Rarely | 613 (17.7) | 22 (20.4) | 635 (17.8) | |
| Sometimes | 911 (26.4) | 33 (30.6) | 944 (26.5) | |
| Often | 453 (13.1) | 22 (20.4) | 475 (13.3) | |
| Walking 100 m | 0.113+ | |||
| Not limited | 3317 (96.5) | 101 (93.5) | 3418 (96.4) | |
| Limited (a little or a lot) | 122 (3.5) | 7 (6.5) | 129 (3.6) | |
| Walking ½ km | 0.049+ | |||
| Not limited | 3204 (93.3) | 95 (88.0) | 3299 (93.2) | |
| Limited (a little or a lot) | 229 (6.7) | 13 (12.0) | 242 (6.8) | |
| Walking 1 km | 0.024+ | |||
| Not limited | 2951 (85.9) | 84 (77.8) | 3035 (85.7) | |
| Limited (a little or a lot) | 483 (14.1) | 24 (22.2) | 507 (14.3) | |
Data presented as n (%) or mean±sd unless otherwise indicated. BMI: body mass index; SF-36 PCS: physical component summary; SF-36 MCS: mental component summary; SEIFA IRSD: Socioeconomic Indexes for Areas index of relative socioeconomic disadvantage. p-values are from: #: two-sample t-test; ¶: Kruskal–Wallis test; +: Fisher's exact test.