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Longitudinal changes in lean mass predict pQCT measures of tibial geometry and mineralisation at 6-7 years
Rebecca J Moon1, Zoe A Cole2, Sarah R Crozier3
1MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK; Paediatric Endocrinology, University Hospital Southampton NHS Foundation Trust, Southampton SO16 6YD, UK.
Insights
Childhood lean mass gain positively impacts bone size and density. Fat mass changes did not show similar bone development associations, highlighting muscle growth as key for childhood bone health.
Area of Science:
- Pediatric Bone Health
- Body Composition Analysis
- Childhood Growth and Development
Background:
- Childhood body composition and early growth influence bone mineral density (BMD).
- Limited understanding exists regarding longitudinal changes in fat mass (FM) and lean mass (LM) and their impact on bone development in pre-pubertal children.
- The Southampton Women's Survey cohort was used to investigate these associations.
Purpose of the Study:
- To investigate the associations between longitudinal changes in body composition (fat mass and lean mass) and bone development in pre-pubertal children.
- To determine whether changes in lean mass or fat mass are more critical for bone development during childhood.
Main Methods:
- Dual-energy x-ray absorptiometry (DXA) assessed total FM and LM at birth and 6-7 years.
- Peripheral quantitative computed tomography (pQCT) measured tibial bone parameters (cross-sectional area, volumetric BMD, cortical properties) at 6-7 years.
- Linear regression analyzed associations between changes in LM/FM (z-scores) and bone parameters, adjusting for confounders and linear growth.
Main Results:
- Increased lean mass (LM) from birth to 7 years was positively associated with tibial total and cortical cross-sectional area (CSA) and trabecular volumetric BMD (vBMD).
- These associations between lean mass gain and bone size/density remained significant after adjusting for linear growth.
- Changes in fat mass (FM) were not significantly associated with bone parameters after adjustment for lean mass and linear growth.
Conclusions:
- Childhood lean mass accrual is a significant positive determinant of bone size and trabecular bone mineral density.
- Changes in fat mass during childhood do not appear to influence bone development.
- Muscle growth, rather than fat accumulation, is suggested as a more critical factor for optimizing childhood bone development.
Background:
Studies in childhood suggest that both body composition and early postnatal growth are associated with bone mineral density (BMD). However, little is known of the relationships between longitudinal changes in fat (FM) and lean mass (LM) and bone development in pre-pubertal children. We therefore investigated these associations in a population-based mother-offspring cohort, the Southampton Women's Survey.
Methods:
Total FM and LM were assessed at birth and 6-7 years of age by dual-energy x-ray absorptiometry (DXA). At 6-7 years, total cross-sectional area (CSA) and trabecular volumetric BMD (vBMD) at the 4% site (metaphysis) of the tibia was assessed using peripheral quantitative computed tomography [pQCT (Stratec XCT-2000)]. Total CSA, cortical CSA, cortical vBMD and strength-strain index (SSI) were measured at the 38% site (diaphysis). FM, LM and bone parameters were adjusted for age and sex and standardised to create within-cohort z-scores. Change in LM (ΔLM) or FM (ΔFM) was represented by change in z-score from birth to 7 years old and conditioned on the birth measurement. Linear regression was used to explore the associations between ΔLM or ΔFM and standardised pQCT outcomes, before and after mutual adjustment and for linear growth. The β-coefficient represents SD change in outcome per unit SD change in predictor.
Results:
DXA at birth, in addition to both DXA and pQCT scans at 6-7 years, were available for 200 children (48.5% male). ΔLM adjusted for ΔFM was positively associated with tibial total CSA at both the 4% (β=0.57SD/SD, p<0.001) and 38% sites (β=0.53SD/SD, p<0.001), cortical CSA (β=0.48SD/SD, p<0.001) and trabecular vBMD (β=0.30SD/SD, p<0.001), but not with cortical vBMD. These relationships persisted after adjustment for linear growth. In contrast, ΔFM adjusted for ΔLM was only associated with 38% total and cortical CSA, which became non-significant after adjustment for linear growth.
Conclusion:
In this study, gain in childhood LM was positively associated with bone size and trabecular vBMD at 6-7 years of age. In contrast, no relationships between change in FM and bone were observed, suggesting that muscle growth, rather than accrual of fat mass, may be a more important determinant of childhood bone development.
