Table I.
Baseline characteristics of subjects in the nested case–control studies of advanced colorectal adenoma and incident colorectal cancer in the PLCO Cancer Screening Trial
| Characteristic | Advanced colorectal adenoma | Colorectal cancer | ||||
|---|---|---|---|---|---|---|
| Cases (n = 1205)a | Controls (n = 1387)a | P-valueb | Cases (n = 370)a | Controls (n = 401)a | P-valueb | |
| Age, years | 63.1±5.3 | 62.6±5.3 | 0.02 | 67.6±6.5 | 67.5±6.3 | 0.78 |
| Gender, n (%) | ||||||
| Male | 776 (64.4) | 888 (64.0) | 0.84 | 218 (58.9) | 242 (60.4) | 0.69 |
| Female | 429 (35.6) | 499 (36.0) | 152 (41.1) | 159 (40.0) | ||
| Ethnicity, n (%) | ||||||
| Non-Hispanic white | 1136 (94.3) | 1284 (92.6) | 0.20 | 337 (91.2) | 363 (90.5) | 0.96 |
| Non-Hispanic black | 29 (2.4) | 47 (3.4) | 18 (4.9) | 21 (5.2) | ||
| Other | 40 (3.3) | 56 (4.0) | 15 (4.1) | 17 (4.2) | ||
| First-degree family history of colorectal cancer, n (%) | 157 (13.1) | 136 (9.9) | 0.03* | 58 (15.8) | 45 (11.4) | 0.20 |
| Education, n (%) | ||||||
| 12 years or less | 416 (34.5) | 399 (28.7) | <0.01* | 139 (37.7) | 113 (28.3) | <0.01* |
| At least some college | 789 (65.5) | 988 (71.3) | 230 (62.3) | 286 (71.9) | ||
| Body mass index (kg/m2) | 27.9±4.7 | 27.4±4.6 | 0.01* | 27.6±4.6 | 27.5±4.9 | 0.78 |
| Hours spent in vigorous physical activity, n (%) | ||||||
| None | 222 (18.5) | 182 (13.2) | <0.001* | 46 (12.4) | 58 (14.5) | 0.88 |
| <1h/week | 216 (18.0) | 229 (16.6) | 73 (19.7) | 72 (18.1) | ||
| 1h/week | 153 (12.7) | 179 (13.0) | 49 (13.2) | 48 (12.0) | ||
| 2h/week | 184 (15.3) | 215 (15.6) | 62 (16.8) | 68 (17.0) | ||
| 3h/week | 184 (15.3) | 212 (15.3) | 54 (14.6) | 66 (16.5) | ||
| 4+ h/week | 242 (20.2) | 365 (26.4) | 86 (23.2) | 87 (21.8) | ||
| Regular use of aspirin or ibuprofen, n (%) | 700 (58.1) | 867 (62.6) | 0.02* | 216 (58.4) | 253 (63.3) | 0.17 |
| Smoking status, n (%) | ||||||
| Never | 462 (38.4) | 657 (47.4) | <0.0001* | 161 (43.5) | 169 (42.1) | 0.93 |
| Former cigarette smoker | 577 (47.9) | 635 (45.8) | 169 (45.9) | 188 (46.9) | ||
| Current cigarette smoker | 165 (13.7) | 95 (6.9) | 40 (10.8) | 44 (11.0) | ||
| Alcohol (g/day) | 15.5±29.0 | 12.1±22.9 | <0.01* | 14.9±30.7 | 11.9±20.8 | 0.12 |
| Total caloric intake (kcal/day) | 2074±805 | 2127±823 | 0.10 | 2087±807 | 2078±768 | 0.87 |
| Dietary fiber (g/1000 kcal) | 11.0±3.4 | 11.7±3.7 | <0.0001* | 11.4±3.6 | 11.6±3.3 | 0.46 |
| Dietary calcium (mg/1000 kcal) | 457±163 | 471±164 | 0.03* | 456±163 | 463±157 | 0.61 |
| Red meat (g/1000 kcal) | 39.9±22.8 | 37.7±23.2 | 0.02* | 37.1±21.0 | 35.8±20.0 | 0.36 |
| Total iron (mg/day)c | 25.4±12.9 | 27.2±13.6 | <0.001* | 26.1±13.7 | 26.6±14.1 | 0.57 |
| Dietary iron (mg/day) | 18.0±8.5 | 19.0±8.7 | <0.01* | 18.3±8.0 | 18.8±9.0 | 0.35 |
| Heme iron (μg/day) | 500±429 | 477±408 | 0.15 | 469±394 | 441±368 | 0.31 |
Data are means ± SDs unless otherwise indicated.
aNumbers may not sum to total due to missing values.
b P-values derived from t test or chi-square test.
cIncludes iron from diet and dietary supplements.
*Statistically significant at P < 0.05.