Table 1.
Selected Baseline Characteristics According to Treatment Assignment.*
| Characteristic | Full Factorial Randomization |
Two-Group Randomization |
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|---|---|---|---|---|---|---|---|---|
| Placebo (N=415) |
Calcium (N=419) |
Vitamin D (N = 420) |
Vitamin D plus Calcium (N = 421) |
Calcium plus Placebo (N = 295) |
Calcium plus Vitamin D (N=289) |
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| Sex— no. (%) | ||||||||
| Female | 60 (14.5) | 63 (15.0) | 62 (14.8) | 67 (15.9) | 295 (100) | 289 (100) | ||
| Male | 355 (85.5) | 356 (85.0) | 358 (85.2) | 354 (84.1) | 0 | 0 | ||
| Age — yr | 58.2±7.0 | 58.7±7.0 | 58.3±7.0 | 58.7±6.9 | 56.7±6.0 | 57.0±6.6 | ||
| Race — no./total no. (%)† | ||||||||
| White | 357/402 (88.8) | 354/404 (87.6) | 364/404 (90.1) | 350/404 (86.6) | 238/275 (86.5) | 237/271 (87.5) | ||
| Black | 27/402 (6.7) | 33/404 (8.2) | 25/404 (6.2) | 46/404(11.4) | 28/275 (10.2) | 25/271 (9.2) | ||
| Asian or Pacific Islander | 10/402 (2.5) | 10/404 (2.5) | 12/404 (3.0) | 6/404 (1.5) | 8/275 (2.9) | 7/271 (2.6) | ||
| Other | 8/402 (2.0) | 7/404 (1.7) | 3/404 (0.7) | 2/404 (0.5) | 1/275 (0.4) | 2/271 (0.7) | ||
| Non-Hispanic ethnic background — no./total no. (%)† | 395/414 (95.4) | 395/418 (94.5) | 396/420 (94.3) | 394/420 (93.8) | 267/295 (90.5) | 263/289 (91.0) | ||
| Family history of colorectal cancer— no./total no. (%) | 59/378 (15.6) | 77/395 (19.5) | 66/391 (16.9) | 75/393 (19.1) | 52/279 (18.6) | 43/270 (15.9) | ||
| BMI‡ | 29.0±4.9 | 29.5±5.1 | 29.1±4.6 | 29.0±5.1 | 28.8±6.0 | 28.3±5.4 | ||
| BMI ≥30— no./total no. (%)‡ | 147/414 (35.5) | 165/419 (39.4) | 163/420 (38.8) | 144/421 (34.2) | 112/294(38.1) | 92/288 (31.9) | ||
| Smoking status — no. (%) | ||||||||
| Never smoked | 187 (45.1) | 212 (50.6) | 217 (51.7) | 204 (48.5) | 205 (69.5) | 169 (58.5) | ||
| Former smoker | 193 (46.5) | 174 (41.5) | 164 (39.0) | 169 (40.1) | 62 (21.0) | 88 (30.4) | ||
| Current smoker | 35 (8.4) | 33 (7.9) | 39 (9.3) | 48 (11.4) | 28 (9.5) | 32(11.1) | ||
| At least one advanced adenoma at baseline — no./total no. (%) |
69/399 (17.3) | 79/399 (19.8) | 80/398 (20.1) | 76/404 (18.8) | 56/289 (19.4) | 47/281 (16.7) | ||
| Alcohol intake — drinks/day | 0.89±1.08 | 0.82±1.01 | 0.91±1.11 | 0.89±1.08 | 0.40±0.72 | 0.48±0.69 | ||
| Dietary calcium intake — mg/day | 672±313 | 718±326 | 643±286 | 652±303 | 604±295 | 656±313 | ||
| Baseline supplemental calcium intake — no./total no. (%)§ | ||||||||
| None | 201/387 (51.9) | 199/393 (50.6) | 207/396 (52.3) | 212/400 (53.0) | 64/257 (24.9) | 56/255 (22.0) | ||
| 1–499 elemental mg/day | 173/387 (44.7) | 172/393 (43.8) | 172/396 (43.4) | 169/400 (42.2) | 94/257 (36.6) | 86/255 (33.7) | ||
| ≥500 elemental mg/day | 13/387 (3.4) | 22/393 (5.6) | 17/396 (4.3) | 19/400 (4.8) | 99/257 (38.5) | 113/255 (44.3) | ||
| Baseline dietary vitamin D intake — lU/day | 138+97 | 146±96 | 131±102 | 130±92 | 124±96 | 134±98 | ||
| Baseline supplemental vitamin D intake — no./total no. (%)§ |
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| None | 204/391 (52.2) | 203/389 (52.2) | 209/397 (52.6) | 210/397 (52.9) | 84/246(34.1) | 71/233 (30.5) | ||
| 1–499 lU/day | 175/391 (44.8) | 170/389 (43.7) | 162/397 (40.8) | 175/397(44.1) | 120/246 (48.8) | 110/233 (47.2) | ||
| ≥500 lU/day | 12/391 (3.1) | 16/389(4.1) | 26/397 (6.5) | 12/397 (3.0) | 42/246(17.1) | 52/233 (22.3) | ||
| Baseline serum 25-hydroxyvitamin D level — ng/ml | 24.24±7.84 | 24.58±8.42 | 24.88±8.09 | 24.45±8.06 | 25.03±8.90 | 24.29±7.71 | ||
| Baseline aspirin use — no. (%) | ||||||||
| <4 days/wk | 255 (61.4) | 249 (59.4) | 255 (60.7) | 270 (64.1) | 227 (76.9) | 206 (71.3) | ||
| ≥4 days/wk | 160 (38.6) | 170 (40.6) | 165 (39.3) | 151 (35.9) | 68 (23.1) | 83 (28.7) | ||
| Baseline non-aspirin NSAID use — no. (%) | ||||||||
| <4 days/wk | 372 (89.6) | 367 (87.6) | 379 (90.2) | 388 (92.2) | 261 (88.5) | 253 (87.5) | ||
| ≥4 days/wk | 43 (10.4) | 52 (12.4) | 41 (9.8) | 33 (7.8) | 34(11.5) | 36 (12.5) | ||
Plus–minus values are means ±SD. The table includes all participants who underwent randomization. Women could elect to be randomly assigned to receive either calcium plus placebo or calcium plus vitamin D (two-group randomization); all other patients were randomly assigned to receive one of four regimens: vitamin D, calcium, both agents, or placebo (full factorial randomization). NSAID denotes nonsteroidal antiinflammatory drug.
Race and ethnic background were self-reported.
The body-mass index (BMI) is the weight in kilograms divided by the square of the height in meters. A BMI of 30 or higher indicates obesity.
Supplemental values include those from separate supplements and multivitamins. Participants were asked to stop taking these personal supplements at enrollment as a condition of study entry. However, from April 2008 onward, daily personal use of up to 1000 IU of vitamin D, 400 mg of elemental calcium, or both were permitted, although discouraged. Patients who wanted to take a multivitamin were offered a special preparation that did not include calcium and vitamin D.