Table 1.
Participant Characteristics
| All Participants at Baseline | Longitudinal Substudy |
|||
|---|---|---|---|---|
| Participants Without 12-mo Data at Baseline | Participants With 12-mo Data |
|||
| Baseline | 12 mo | |||
| n | 594 | 210 | 145 | 145 |
| Age, y | 12.3 ± 4.0 | 13.7 ± 4.4 | 14.1 ± 4.3 | |
| Age range, y | 5.0–21.9 | 5.3–21.9 | 5.3–21.9 | |
| Female sex, n (%) | 291 (49) | 101 (48) | 71 (49) | |
| Race, n (%) | ||||
| White | 290 (49) | 133 (63) | 101 (70) | |
| Black | 242 (41) | 57 (27) | 30 (21) | |
| Other | 62 (10) | 20 (10) | 14 (9) | |
| Tanner stage, n (%) | ||||
| I | 187 (31) | 51 (24) | 29 (20) | 19 (13) |
| II | 69 (12) | 22 (11) | 16 (11) | 12 (8) |
| III | 80 (13) | 19 (9) | 7 (5) | 15 (11) |
| IV | 139 (23) | 56 (27) | 47 (33) | 35 (24) |
| V | 119 (20) | 61 (29) | 45 (31) | 64 (44) |
| Height, cm | 150.6 ± 18.9 | 155.7 ± 18.0 | 157.7 ± 16.7 | 161.2 ± 14.8c |
| Height Z-score | 0.28 ± 0.93 | 0.34 ± 0.88 | 0.36 ± 0.83 | 0.37 ± 0.82 |
| BMI, kg/m2 | 20.0 (17.5, 23.3) | 20.7 (17.6, 23.3) | 20.0 (17.6, 23.1) | 20.6 (18.3, 23.2)c |
| BMI Z-score | 0.38 ± 1.02 | 0.32 ± 1.03 | 0.27 ± 0.96 | 0.27 ± 0.98 |
| Winter season, n (%) | 214 (36) | 85 (41) | 59 (41) | |
| Calcium intake, mg/da | 799 (577, 1057) | 856 (629, 1117) | 857 (629, 1098) | |
| Laboratory studies | ||||
| PTH, pg/mL | 30 (21, 42) | 29 (22, 41) | 29 (22, 43) | |
| 25(OH)D, ng/mL | b | 23.1 (16.6, 28.0) | 23.1 (17.4, 27.9) | |
| 25(OH)D < 20 ng/mL, n (%) | b | |||
| Black race | 41 (72) | 24 (80) | ||
| Non-black race | 40 (26) | 32 (28) | ||
| 1,25(OH)2D, pg/mL | b | 39.2 (34, 47.3) | 39.3 (33.5, 46.8) | |
| BSAP, μg/L | 69.2 (31.2, 94.2) | 47.7 (16.7, 84.2) | 34.5 (16.1, 80.7) | |
| DPD, nmol/mmol creatinine | 54.8 (28.1, 71.4) | 47.0 (21.1, 66.4) | 42.5 (21.6, 65.6) | |
| Imaging studies | ||||
| DXA subtotal BMC, g | 1120 (680, 1535) | 1334 (819, 1721) | 1386 (957, 1731) | 1465 (1198, 1818)c |
| pQCT cortical BMC, mg | 256 (184, 321) | 274 (217, 333) | 275 (228, 329) | 299 (251, 356)c |
| pQCT cortical BMD, mg/cm3 | 1098 (1064, 1143) | 1115 (1067, 1162) | 1116 (1066, 1162) | 1136 (1076, 1171)c |
Data are presented as mean ± SD or median (interquartile range), unless stated otherwise.
a
Dietary calcium intake data available in 530 of the overall sample, 155 of the 210 participants in the substudy at baseline, and 102 of those with longitudinal data.
b
Vitamin D data available in only the 210 participants in the longitudinal substudy due to differences in assays.
c
P < .001 compared to baseline measure.