Table 1.
Characteristics of the Study Participants.*
| Characteristic | Flexible-Sigmoidoscopy Group (N = 77,445) | Usual-Care Group (N = 77,455) |
| no. of participants (%) | ||
| Sex | ||
| Female | 39,105 (50.5) | 39,111 (50.5) |
| Male | 38,340 (49.5) | 38,344 (49.5) |
| Age | ||
| 55–59 yr | 25,851 (33.4) | 25,839 (33.4) |
| 60–64 yr | 23,783 (30.7) | 23,771 (30.7) |
| 65–69 yr | 17,457 (22.5) | 17,473 (22.6) |
| 70–74 yr | 10,354 (13.4) | 10,372 (13.4) |
| Race or ethnic group† | ||
| White (non-Hispanic) | 66,874 (86.4) | 65,708 (84.8) |
| Black (non-Hispanic) | 3,883 (5.0) | 3,825 (4.9) |
| Hispanic | 1,421 (1.8) | 1,397 (1.8) |
| Asian | 2,791 (3.6) | 2,785 (3.6) |
| Other or unknown | 2,476 (3.2) | 3,740 (4.8) |
| Educational level | ||
| High-school graduate or less | 22,892 (29.6) | 22,583 (29.2) |
| Some college | 25,935 (33.5) | 25,585 (33.0) |
| College graduate | 26,659 (34.4) | 25,915 (33.5) |
| Unknown | 1,959 (2.5) | 3,372 (4.4) |
| Prior FOBT‡ | ||
| Yes | 29,244 (37.8) | 29,890 (38.6)§ |
| No | 43,858 (56.6) | 42,223 (54.5) |
| Unknown | 4,343 (5.6) | 5,342 (6.9) |
| Prior lower GI endoscopy¶ | ||
| Yes | 9,736 (12.6) | 10,113 (13.1)§ |
| No | 64,653 (83.5) | 62,997 (81.3) |
| Unknown | 3,056 (3.9) | 4,345 (5.6) |
| Either prior FOBT or prior lower GI endoscopy | ||
| Yes | 31,511 (40.7) | 31,990 (41.3)§ |
| No | 40,648 (52.5) | 39,161 (50.6) |
| Unknown | 5,286 (6.8) | 6,304 (8.1) |
| First-degree relative with colorectal cancer | ||
| Yes | 7,643 (9.9) | 7,322 (9.5) |
| No | 65,299 (84.3) | 64,506 (83.3) |
| Unknown | 4,503 (5.8) | 5,627 (7.3) |
| Daily use of aspirin or ibuprofen in past 12 mo | ||
| Yes | 24,822 (32.1) | 23,949 (30.9)‖ |
| No | 50,368 (65.0) | 49,766 (64.3) |
| Unknown | 2,255 (2.9) | 3,740 (4.8) |
| Aspirin or ibuprofen use ≥3–4 times per wk in past 12 mo | ||
| Yes | 33,248 (42.9) | 32,087 (41.4)** |
| No | 41,971 (54.2) | 41,658 (53.8) |
| Unknown | 2,226 (2.9) | 3,710 (4.8) |
*
There were no significant differences between the groups except as noted. FOBT denotes fecal occult-blood test, and GI gastrointestinal.
†
Race or ethnic group was determined by self-report.
‡
Prior FOBT indicates a test within 3 years before study entry.
§
P<0.001
¶
Prior lower GI endoscopy indicates sigmoidoscopy, colonoscopy, or barium enema examination within 3 years before randomization.
‖
P = 0.03
**
P = 0.01