Table 1.
Baseline characteristics of D2d participantsa.
| Overall (n = 2423) | Vitamin D3 (n = 1211) | Placebo (n = 1212) | |
|---|---|---|---|
| Characteristic | |||
| Age, years | 60.0 ± 9.9 | 59.6 ± 9.9 | 60.4 ± 10.0 |
| Women, no. (%) | 1086 (44.8) | 541 (44.7) | 545 (45.0) |
| Race, no. (%)b | |||
| Asian | 130 (5.4) | 66 (5.5) | 64 (5.3) |
| Black or African American | 616 (25.4) | 301 (24.9) | 315 (26.0) |
| White | 1616 (66.7) | 810 (66.9) | 806 (66.5) |
| Other | 61 (2.5) | 34 (2.8) | 27 (2.3) |
| Hispanic or Latino Ethnicity, no. (%)b | 225 (9.3) | 120 (9.9) | 105 (8.7) |
| Body-mass index, kg/m2 | 32.1 ± 4.5 | 32.0 ± 4.5 | 32.1 ± 4.4 |
| Health history | |||
| Medical conditions, no. (%) | |||
| Hypercholesterolemia | 1346 (55.6) | 661 (54.6) | 685 (56.5) |
| Cancerc | 262 (10.8) | 126 (10.4) | 136 (11.2) |
| Cardiovascular diseased | 305 (12.6) | 106 (9.8) | 199 (14.9) |
| Hypertension | 1297 (53.5) | 622 (51.4) | 675 (55.7) |
| Dietary supplementse | |||
| Vitamin D | |||
| Participants taking vitamin D supplements, no. (%) | 1037 (42.8) | 508 (41.9) | 529 (43.6) |
| Vitamin D intake among all participants, IU/dayf | 313 ± 398 | 310 ± 401 | 316 ± 397 |
| Vitamin D intake among participants using supplements, IU/day | 732 ± 254 | 739 ± 256 | 725 ± 253 |
| Calcium | |||
| Participants taking calcium supplements, no. (%) | 804 (33.2) | 385 (31.8) | 419 (34.6) |
| Calcium intake among all participants, mg/dayf | 103 ± 176 | 100 ± 175 | 107 ± 176 |
| Calcium intake among participants using supplements, mg/day | 312 ± 167 | 316 ± 168 | 308 ± 166 |
| Laboratory | |||
| Serum 25-hydroxyvitamin D | |||
| Mean, ng/mL | 28.0 ± 10.2 | 27.7 ± 10.2 | 28.2 ± 10.1 |
| Distribution, no. (%) | |||
| <12 ng/mL | 103 (4.3) | 60 (5.0) | 43 (3.6) |
| 12–19 ng/mL | 422 (17.4) | 216 (17.8) | 206 (17.0) |
| 20–29 ng/mL | 876 (36.2) | 453 (37.4) | 423 (34.9) |
| ≥30 ng/mL | 1021 (42.2) | 482 (39.8) | 539 (44.5) |
| Serum calcium, mg/dL | 9.41 ± 0.37 | 9.40 ± 0.37 | 9.41 ± 0.38 |
| Estimated glomerular filtration rate, mL/min/1.73 mb, g | 87.1 ± 15.7 | 87.5 ± 15.6 | 86.7 ± 15.9 |
| Fasting urine calcium-creatinine ratio | 0.09 ± 0.06 | 0.09 ± 0.06 | 0.08 ± 0.06 |
| Hematocrit, %h | 42.8 ± 3.5 | 42.8 ± 3.4 | 42.8 ± 3.5 |
aPlus-minus values are means ± SD. Percentages may not add up to 100 because of rounding. To convert 25-hydroxyvitamin D from ng/mL to nmol/L, multiply by 2.456; to convert vitamin D intake from IU to mcg, divide by 40.
bRace and ethnicity were reported by the participant. The category “other” includes American Indian or Alaska Native; Native Hawaiian or other Pacific Islander; or other race. Ethnicity includes any race.
cCancer (except for basal cell skin cancer) within 5 years of randomization was an exclusion criterion. Prostate cancer or well-differentiated thyroid cancer not expected to require treatment over the next 4 years were not exclusions. Persons with history of squamous cell cancer of the skin, which was completely excised and with no evidence of metastases, were eligible.
dCardiovascular disease included: arrhythmias, chest pain, congestive heart failure, coronary artery disease, CABG/PCI, myocardial infarction, palpitations, peripheral vascular disease.
eData on vitamin D and calcium intake are derived from a question about supplements, including multivitamins and high-dose prescribed doses. Participants were allowed to take, from supplements, up to 1000 IU/day of vitamin D and 600 mg/day of calcium. Dietary intake of vitamin D and calcium was not limited.
fValue shown is among all participants regardless of whether they reported use of supplements or not.
gBased on the Chronic Kidney Disease Epidemiology Collaboration equation.
hIndividuals were excluded if they had anemia at screening visit defined as hematocrit <32% for women, <36% for men.