TABLE 2.
Associations between total-body fat mass and TBLH BA or TBLH BMC at age 9.9 yr calculated by multivariable linear regression on 3082 boys and girls
| Variables in regression model | n | Fat mass vs. TBLH bone area at age 9.9 yr |
Fat mass vs. TBLH BMC at age 9.9 yr |
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|---|---|---|---|---|---|---|---|
| Coefficient (95% CI) | P value | R2 | Coefficient (95% CI) | P value | R2 | ||
| Model 1: age, ethnicity, and socioeconomic status | |||||||
| Boys and girls | 3082 | 0.693 (0.666-0.720) | <0.001 | 0.463 | 0.673 (0.645-0.700) | <0.001 | 0.441 |
| Boys | 1398 | 0.624 (0.583-0.666) | <0.001 | 0.605 (0.562-0.647) | <0.001 | ||
| Tanner stage 1 girls | 1085 | 0.755 (0.697-0.812) | <0.001 | 0.714 (0.657-0.771) | <0.001 | ||
| Tanner stage 2 girls | 508 | 0.674 (0.603-0.746) | <0.001 | 0.646 (0.574-0.718) | <0.001 | ||
| Tanner stage 3 girls | 91 | 0.599 (0.473-0.725) | <0.001 | 0.593 (0.466-0.721) | <0.001 | ||
| Model 1 and height | |||||||
| Boys and girls | 3082 | 0.383 (0.364-0.401) | <0.001 | 0.801 | 0.388 (0.367-0.410) | <0.001 | 0.727 |
| Boys | 1398 | 0.321 (0.294-0.348) | <0.001 | 0.326 (0.293-0.359) | <0.001 | ||
| Tanner stage 1 girls | 1085 | 0.426 (0.387-0.465) | <0.001 | 0.421 (0.377-0.466) | <0.001 | ||
| Tanner stage 2 girls | 508 | 0.434 (0.387-0.482) | <0.001 | 0.417 (0.364-0.470) | <0.001 | ||
| Tanner stage 3 girls | 91 | 0.414 (0.326-0.501) | <0.001 | 0.430 (0.327-0.532) | <0.001 | ||
| Model 1 and lean mass | |||||||
| Boys and girls | 3082 | 0.281 (0.264-0.299) | <0.001 | 0.838 | 0.271 (0.252-0.291) | <0.001 | 0.799 |
| Boys | 1398 | 0.249 (0.224-0.274) | <0.001 | 0.238 (0.209-0.267) | <0.001 | ||
| Tanner stage 1 girls | 1085 | 0.278 (0.241-0.315) | <0.001 | 0.260 (0.220-0.301) | <0.001 | ||
| Tanner stage 2 girls | 508 | 0.334 (0.286-0.383) | <0.001 | 0.309 (0.258-0.361) | <0.001 | ||
| Tanner stage 3 girls | 91 | 0.381 (0.297-0.465) | <0.001 | 0.375 (0.289-0.461) | <0.001 | ||
| Model 1 and height and lean mass | |||||||
| Boys and girls | 3082 | 0.274 (0.258-0.290) | <0.001 | 0.871 | 0.266 (0.247-0.285) | <0.001 | 0.815 |
| Boys | 1398 | 0.234 (0.212-0.256) | <0.001 | 0.228 (0.200-0.256) | <0.001 | ||
| Tanner stage 1 girls | 1085 | 0.276 (0.243-0.309) | <0.001 | 0.259 (0.220-0.297) | <0.001 | ||
| Tanner stage 2 girls | 508 | 0.344 (0.300-0.388) | <0.001 | 0.317 (0.268-0.366) | <0.001 | ||
| Tanner stage 3 girls | 91 | 0.367 (0.290-0.444) | <0.001 | 0.368 (0.283-0.454) | <0.001 | ||
Coefficients with 95% confidence intervals (CI) were calculated for each of the four regression models shown, using standardized continuous variables (minus mean, divided by SD) for fat mass, TBLH bone area, TBLH BMC, height, and lean mass. Coefficients are therefore per SD increase in dependent variable. R2 is the adjusted R2 for each model with the boys and girls combined. In the final model for the association between fat mass and TBLH bone area for boys and girls combined, the coefficient for height is 0.315 (95% CI, 0.293-0.337) and for lean mass is 0.511 (95% CI, 0.487-0.536). In the final model for the association between fat mass and TBLH BMC, the coefficient for height is 0.219 (95% CI, 0.193-0.245) and for lean mass is 0.573 (95% CI, 0.544-0.602).