Table 3. Association of Body Fat (Model 1) and Lean Mass (Model 2) with Growth and Bone Health, adjusting for Age, Sex, Ethnicity, Transfusion status, Calcium intake and Physical activity in Patients with Thalassemia (n=370).
| Model 1 | Model 2 | ||||||
|---|---|---|---|---|---|---|---|
| Outcome | Predictor | Slope | Standard Error | P-value^^ | Slope | Standard Error | P-value ^^ |
| Height Z-score | Age, years | −0.03 | 0.01 | <0.001 | −0.03 | 0.01 | <0.001 |
| Sex (F vs. M)* | −0.24 | 0.13 | 0.058 | 0.27 | 0.13 | 0.04 | |
| Transfusion Status (Tx vs NTx)** | −0.71 | 0.14 | <0.001 | −0.56 | 0.14 | <0.001 | |
| Asian Ethnicity*** | −0.46 | 0.14 | 0.004 | −0.42 | 0.14 | 0.01 | |
| Calcium Dietary Reference Intake (one unit is 100%) |
−0.01 | 0.07 | NS | 0.01 | 0.07 | NS | |
| Very Active Physical Activity Level# | 0.44 | 0.29 | NS | 0.42 | 0.29 | NS | |
| Body Fat, kg ^ | 0.06 | 0.01 | <0.001 | -- | -- | -- | |
| Lean Mass, kg ^ | -- | -- | -- | 0.04 | 0.01 | <0.001 | |
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Bone Mineral
Density Z-score |
Age, years | −0.05 | 0.01 | <0.001 | −0.05 | 0.01 | <0.001 |
| Gender (F vs M)* | −0.06 | 0.12 | NS | 0.21 | 0.13 | NS | |
| Transfusion Status (Tx vs NTx)** | −0.47 | 0.14 | <0.001 | −0.36 | 0.14 | 0.009 | |
| Asian Ethnicity*** | −0.16 | 0.13 | NS | −0.16 | 0.13 | NS | |
| Calcium Dietary Reference Intake (one unit is 100%) |
−0.12 | 0.06 | NS | −0.13 | 0.07 | 0.052 | |
| Very Active Physical Activity Level# | 0.72 | 0.27 | 0.01 | 0.68 | 0.28 | 0.04 | |
| Body Fat, kg ^ | 0.04 | 0.01 | <0.001 | -- | -- | -- | |
| Lean Mass, kg ^ | -- | -- | -- | 0.02 | 0.01 | 0.01 | |
Sex: Female vs. Male (reference). Male sex is negatively associated with height z-score when body fat is in the model, but was positively associated with height when lean mass is in the model. This inverse relationship is likely a reflection of the relative amount of fat mass vs. lean in females compared with males.
Transfusion status: transfused vs. non-transfused (reference) subjects with thalassemia
Ethnicity: Asian, Other, Caucasian (reference)
Physical Activity estimated by self assessment Likert scale: Very Lightly (reference), Lightly, Moderately, Active, Very Active
Body fat and lean mass determined by whole body DXA
Multiple linear regression analysis was used to examine the association of variables of interest with growth and with bone health. Even after adjusting for other covariates, the two body composition variables were each significantly (p-value<0.05) associated with the outcome variable. For example, as predicted in the model above, Height Z-score is expected to increase by 0.04 units for every 1 kg increase in lean mass in the subjects with thalassemia studied.