Characteristics of the study population and participation rates between different groups
| Factors | Participants of high risk for colorectal cancer (%) | Participants undertaking colonoscopy (%) | Participation rate (%) | P values* |
| Age (years) | ||||
| 40–44 | 21 879 (12.0) | 2650 (10.4) | 12.1 | <0.001 |
| 45–49 | 30 805 (16.8) | 4300 (16.8) | 14.0 | |
| 50–54 | 36 576 (20.0) | 5454 (21.3) | 14.9 | |
| 55–59 | 35 266 (19.3) | 5142 (20.1) | 14.6 | |
| 60–64 | 35 563 (19.4) | 5041 (19.7) | 14.2 | |
| 65–69 | 22 838 (12.5) | 3006 (11.7) | 13.2 | |
| Sex | ||||
| Men | 80 322 (43.9) | 14 416 (43.7) | 13.9 | <0.001 |
| Women | 102 605 (56.1) | 11 177 (56.3) | 14.1 | |
| Educational background | ||||
| Low | 23 370 (12.8) | 2994 (11.7) | 12.8 | <0.001 |
| Intermediate | 120 609 (65.9) | 16 189 (63.3) | 13.4 | |
| High | 38 948 (21.3) | 6410 (25.0) | 16.5 | |
| Smoking | ||||
| Non-smoker | 108 765 (59.5) | 15 208 (59.4) | 14.0 | <0.001 |
| Current smoker | 62 875 (34.4) | 8487 (33.2) | 13.5 | |
| Past smoker | 11 287 (6.2) | 1898 (7.4) | 16.8 | |
| Past faecal occult blood test | ||||
| No | 146 082 (79.9) | 19 887 (77.7) | 13.6 | <0.001 |
| Yes (positive result) | 13 721 (7.5) | 2364 (9.2) | 17.2 | |
| Yes (negative result) | 15 365 (8.4) | 2039 (8.0) | 13.3 | |
| Yes (unknown result) | 7759 (4.2) | 1303 (5.1) | 16.8 | |
| Family history of colorectal cancer | ||||
| No | 141 026 (77.1) | 16 823 (65.7) | 11.9 | <0.001 |
| Yes | 41 901 (22.9) | 8770 (34.3) | 20.9 | |
| Previously detected colonic polyp | ||||
| No | 137 909 (75.7) | 16 762 (65.7) | 12.2 | <0.001 |
| Yes | 44 265 (24.3) | 8735 (34.3) | 19.7 | |
↵*P values for the differences in participation rate of different groups by the χ2 test.