Table 3.
Rates of change in outcomes estimated by mixed effects model by sex and program status
| Rate of change of outcome (per year) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Males & Females | Males | Females | ||||||||
| Outcome of each model | Group indicator a | Rate of change (unit/year) | Standard error | p-value vs. Ca | Rate of change (unit/year) | Standard error | p-value vs. Ca | Rate of change (unit/year) | Standard error | p-value vs. Ca |
| BMI z-score | B + P | 0.02322 | 0.02401 | 0.1292 | 0.03198 | 0.04089 | 0.1886 | 0.01316 | 0.02422 | 0.4654 |
| B | 0.04661 | 0.03001 | 0.3969 | 0.08685 | 0.04747 | 0.6667 | 0.00321 | 0.03359 | 0.3984 | |
| C | 0.08362** | 0.03161 | – | 0.11626* | 0.04888 | – | 0.04514 | 0.03636 | – | |
| Percent body fat (%) | B + P | 1.3784** | 0.4691 | 0.2319 | 1.7398** | 0.5517 | 0.0265 | 1.1805* | 0.4845 | 0.8099 |
| B | 1.8076** | 0.5588 | 0.1021 | 2.2980*** | 0.6407 | 0.0076 | 1.8399** | 0.6219 | 0.6313 | |
| C | 0.4771 | 0.5882 | – | −0.1397 | 0.6306 | – | 1.3871 | 0.7070 | – | |
| Calcium-rich food knowledge score | B + P | 0.4788*** | 0.0855 | 0.9342 | 0.4306** | 0.1425 | 0.8080 | 0.4897*** | 0.1151 | 0.7887 |
| B | 0.7524*** | 0.1097 | 0.0680 | 0.7004*** | 0.1660 | 0.3458 | 0.7848*** | 0.1572 | 0.1333 | |
| C | 0.4672*** | 0.1104 | – | 0.4827** | 0.1593 | – | 0.4345* | 0.1706 | – | |
| Physical activity knowledge score | B + P | 32.88*** | 8.27 | 0.5947 | 35.96** | 12.58 | 0.5123 | 29.99** | 10.95 | 0.9289 |
| B | 44.58*** | 10.56 | 0.2088 | 40.46** | 15.14 | 0.4153 | 48.81** | 14.72 | 0.3449 | |
| C | 25.70* | 10.64 | – | 23.43 | 14.33 | – | 28.26 | 15.92 | – | |
| Calcium-rich food preference score | B + P | 0.1084 | 0.0619 | 0.8224 | 0.1353 | 0.0938 | 0.5823 | 0.0948 | 0.0835 | 0.8278 |
| B | 0.1088 | 0.0795 | 0.8375 | 0.0668 | 0.1115 | 0.9517 | 0.1313 | 0.1144 | 0.9816 | |
| C | 0.0857 | 0.0800 | – | 0.0575 | 0.1053 | – | 0.1274 | 0.1240 | – | |
| Total calcium intake | B + P | −9.58 | 42.35 | 0.4939 | −14.39 | 55.73 | 0.5383 | −22.70 | 46.75 | 0.6603 |
| B | 15.62 | 52.08 | 0.7695 | −33.04 | 65.98 | 0.4407 | 47.57 | 62.68 | 0.7301 | |
| C | 37.75 | 54.57 | – | 37.68 | 63.32 | – | 14.79 | 71.10 | – | |
| Trimmed calcium intake (< 2500 for age up to 9, < 3000 for age > =9) | B + P | −6.44 | 38.28 | 0.3339 | −20.00 | 50.79 | 0.2724 | −7.26 | 44.34 | 0.7929 |
| B | 3.87 | 47.67 | 0.4653 | −35.06 | 51.23 | 0.2377 | 24.60 | 59.38 | 0.9050 | |
| C | 54.06 | 49.38 | – | 64.94 | 57.88 | – | 13.89 | 67.01 | – | |
| MET score | B + P | 1.8873** | 0.6772 | 0.0026 | 1.6754 | 1.0115 | 0.0039 | 2.0405* | 0.8800 | 0.3259 |
| B | 0.8487 | 0.5874 | 0.0596 | 1.7086 | 1.2161 | 0.0076 | −0.1833 | 1.1811 | 0.6910 | |
| C | −1.4592 | 0.8682 | – | −2.8420* | 1.1566 | – | 0.5103 | 1.2797 | – | |
| WBF score | B + P | 0.4746*** | 0.1349 | 0.0019 | 0.5125* | 0.2052 | 0.0010 | 0.4260* | 0.1753 | 0.5584 |
| B | 0.2317 | 0.1708 | 0.0679 | 0.4448 | 0.2454 | 0.0046 | 0.0037 | 0.2349 | 0.4753 | |
| C | −0.2141 | 0.1731 | – | − 0.5335* | 0.2339 | – | 0.2445 | 0.2550 | – | |
| Grip strength (kg) | B + P | 1.2406*** | 0.1461 | 0.6682 | 1.0568*** | 0.1802 | 0.9395 | 1.3980*** | 0.1709 | 0.4730 |
| B | 1.0055*** | 0.1787 | 0.6049 | 1.0356*** | 0.2122 | 0.9988 | 1.0197*** | 0.2244 | 0.6379 | |
| C | 1.1391*** | 0.1861 | – | 1.0361*** | 0.2050 | – | 1.1789*** | 0.2522 | – | |
| Vertical jump (in) | B + P | 0.6154*** | 0.1473 | 0.6493 | 0.6276*** | 0.1773 | 0.8487 | 0.5810** | 0.1747 | 0.3824 |
| B | 0.2651 | 0.1780 | 0.0759 | 0.0243 | 0.2089 | 0.0601 | 0.5269* | 0.2237 | 0.3414 | |
| C | 0.7233*** | 0.1857 | – | 0.5761** | 0.2027 | – | 0.8497** | 0.2538 | – | |
| Bone stiffness | B + P | 0.5682 | 0.8032 | 0.0506 | −1.6887 | 1.4825 | 0.4189 | 2.0487* | 0.8608 | 0.0995 |
| index (3 groups) | B | −0.2319 | 1.1187 | 0.2368 | −4.0010 | 2.0555 | 0.8523 | 2.0957 | 1.1986 | 0.1386 |
| C | −2.0669 | 1.0574 | – | −3.5066* | 1.6495 | – | −0.5761 | 1.3078 | – | |
| Bone stiffness | B + P/B | 0.3026 | 0.6527 | 0.0603 | −2.4862* | 1.2067 | 0.6204 | 2.0757** | 0.6990 | 0.0797 |
| index (2 groups) | C | −2.0670 | 1.0584 | – | −3.5101* | 1.6554 | – | −0.5754 | 1.3078 | – |
Abbreviations: B + P BONES + Parent, B BONES, C Control, BMI body mass index, MET metabolic equivalent time, WBF weight-bearing factor
Adjusted for time point, baseline age, and race/ethnicity (white, black, Hispanic, others); adjusted for individual nested within after-school program as cluster effects
In total, 2476 observations were made in the three time points. Numbers of observations used in the above analysis range from 1828 (74%) to 1902 (77%) for all the outcomes except bone stiffness. For bone stiffness, the number of observation used in the analysis is 981 (40%)
ap vs. C: p-value of the difference between the slopes of the intervention (B + P or B) and the control group
* p < 0.05; ** p < 0.01; *** p < 0.001; these p-values indicate if the rate of change is significantly different from zero