Table 1 Demographics of Control, ‘COPD Risk (undiagnosed)’ and ‘COPD Diagnosed’ groups
|  | All | Control group | ‘COPD Risk (undiagnosed)’ group | ‘COPD Diagnosed’ group | Risk vs. Control, p value | Diagnosed vs. Control, p value | Risk vs. Diagnosed, p value |
|---|---|---|---|---|---|---|---|
|  | (n = 19,994) | (n = 16,161) | (n = 3320) | (n = 513) |  |  |  |
Gender, n (%) | < 0.001 | < 0.001 | < 0.001 | ||||
 Female | 9994 (50.0) | 8628 (53.4) | 1135 (34.2) | 231 (45.0) |  |  |  |
 Male | 10,000 (50.0) | 7533 (46.6) | 2185 (65.8) | 282 (55.0) |  |  |  |
Age in years, n (%) | 0.000 | < 0.001 | < 0.001 | ||||
 18–39 | 8369 (41.9) | 7717 (47.8) | 462 (13.9) | 190 (37.0) |  |  |  |
 40–59 | 7942 (39.7) | 6491 (40.2) | 1254 (37.8) | 197 (38.4) |  |  |  |
 60+ | 3683 (18.4) | 1953 (12.1) | 1604 (48.3) | 126 (24.6) |  |  |  |
Marital status, n (%) | < 0.001 | 0.413 | < 0.001 | ||||
 Married or living with partner | 16,004 (80.0) | 12,640 (78.2) | 2951 (88.9) | 413 (80.5) |  |  |  |
 Not married | 3954 (19.8) | 3496 (21.6) | 358 (10.8) | 100 (19.5) |  |  |  |
 Decline to answer | 36 (0.18) | 25 (0.15) | 11 (0.33) | 0 (0.00) |  |  |  |
Education, n (%) | < 0.001 | < 0.001 | < 0.001 | ||||
 Less than university degree | 8312 (41.6) | 5849 (36.2) | 2200 (66.3) | 263 (51.3) |  |  |  |
 University (4 years) degree or higher | 11,635 (58.2) | 10,277 (63.6) | 1109 (33.4) | 249 (48.5) |  |  |  |
 Decline to answer | 47 (0.24) | 35 (0.22) | 11 (0.33) | 1 (0.19) |  |  |  |
Household income (after tax/welfare), n (%) | < 0.001 | 0.880 | < 0.001 | ||||
 CNY 7999 or below | 13,606 (68.1) | 10,718 (66.3) | 2544 (76.6) | 344 (67.1) |  |  |  |
 CNY 8000–15,999 | 4809 (24.1) | 4083 (25.3) | 598 (18.0) | 128 (25.0) |  |  |  |
 CNY 16,000 or above | 1321 (6.61) | 1136 (7.03) | 149 (4.49) | 36 (7.02) |  |  |  |
 Decline to answer | 258 (1.29) | 224 (1.39) | 29 (0.87) | 5 (0.97) |  |  |  |
Employment, n (%) | < 0.001 | < 0.001 | < 0.001 | ||||
 Not employed | 5105 (25.5) | 3276 (20.3) | 1661 (50.0) | 168 (32.7) |  |  |  |
 Currently employed | 14,889 (74.5) | 12,885 (79.7) | 1659 (50.0) | 345 (67.3) |  |  |  |