Table 2.
Baseline Characteristics of Participants in all Clinical Trials
| Characteristic | Placebo | Folic Acid |
|---|---|---|
| Number of participants | 1308 | 1324 |
|
| ||
| Trial, no. (%) | ||
| AFPPS | 505 (39) | 516 (39) |
| NHS/HPFS | 334 (26) | 338 (26) |
| ukCAP | 469 (36) | 470 (36) |
|
| ||
| Age, yr | 59.7 ± 9.5 | 59.3 ± 9.4 |
| ≤57, no. (%) | 524 (40) | 533 (40) |
| 58–65, no. (%) | 381 (29) | 411 (31) |
| ≥66, no. (%) | 403 (31) | 380 (29) |
|
| ||
| Male sex, no. (%) | 717 (55) | 726 (55) |
|
| ||
| Body mass index (kg/m2) | 26.7 ± 4.3 | 26.7 ± 4.4 |
| <25.0, no. (%) | 417 (32) | 442 (33) |
| 25.0–29.9, no. (%) | 502 (38) | 497 (38) |
| ≥30, no. (%) | 212 (16) | 217 (16) |
| Unknown, no. (%) | 177 (14) | 168 (13) |
|
| ||
| Race or ethnic group, no. (%) | ||
| White | 1040 (80) | 1073 (81) |
| Black | 39 (3) | 31 (2) |
| Hispanic | 24 (2) | 31 (2) |
| Other | 29 (2) | 25 (2) |
| Unknown | 176 (13) | 164 (12) |
|
| ||
| Tobacco smoking status, no (%) | ||
| Never smoker | 443 (34) | 449 (34) |
| Former smoker | 515 (39) | 529 (40) |
| Current smoker | 171 (13) | 176 (13) |
| Unknown | 179 (14) | 170 (13) |
|
| ||
| Family history of colorectal cancer, no. (%) | ||
| No known history | 708 (54) | 747 (56) |
| First-degree relative | 326 (25) | 310 (23) |
| Unknown | 274 (21) | 267 (20) |
|
| ||
| Number of adenomas at baseline exam, no. (%) | ||
| 1 | 533 (41) | 575 (43) |
| ≥2 | 398 (30) | 378 (29) |
| Unknown | 43 (3) | 33 (2) |
| Not collected (NHS/HPFS) | 334 (26) | 338 (26) |
|
| ||
| Advanced adenoma* at baseline exam, no. (%) | ||
| No | 413 (32) | 420 (32) |
| Yes | 515 (39) | 531 (51) |
| Unknown | 46 (4) | 35 (3) |
|
| ||
| Not collected (NHS/HPFS) | 334 (26) | 338 (26) |
| Randomized aspirin treatment, no. (%) | ||
| Placebo | 402 (31) | 404 (31) |
| 81 mg | 169 (13) | 175 (13) |
| 300 mg | 236 (18) | 236 (18) |
| 325 mg | 167 (13) | 171 (13) |
| Not randomized (NHS/HPFS) | 334 (26) | 338 (26) |
|
| ||
| Alcohol intake (drinks/day) | 0.85 ± 1.32 | 0.85 ± 1.29 |
| non-drinker, no. (%) | 308 (24) | 313 (24) |
| ≤1, no. (%) | 571 (44) | 557 (42) |
| >1 and <2, no. (%) | 133 (10) | 159 (12) |
| ≥2, no. (%) | 158 (12) | 165 (12) |
| Unknown, no. (%) | 138 (11) | 130 (10) |
|
| ||
| Dietary Folate (mcg/day) | 316 ± 133 | 317 ± 128 |
| ≤ 232, no. (%) | 264 (20) | 268 (20) |
| 233–304, no. (%) | 264 (20) | 263 (20) |
| 305–378 | 251 (19) | 275 (21) |
| > 378, no. (%) | 258 (20) | 267 (20) |
| unknown, no. (%) | 271 (21) | 251 (19) |
|
| ||
| Baseline Plasma Folate (nmol/L) | 22.5 ± 15.8 | 23.0 ± 16.9 |
| ≤ 11, no. (%) | 197 (15) | 197 (15) |
| 11.1–18, no. (%) | 188 (14) | 200 (15) |
| 18.1–29, no. (%) | 198 (15) | 195 (15) |
| > 29, no. (%) | 196 (15) | 203 (15) |
| unknown, no. (%) | 60 (5) | 59 (6) |
| not measured (ukCAP) | 469 (36) | 470 (35) |
Plus-minus values are mean ± SD
*
defined as invasive carcinoma or adenomas with any mention of villous component, high grade dysplasia, or estimated size of 1 centimeter or greater.