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Bone, 2015; 75(): 105-10, PMID: 25703480

Longitudinal changes in lean mass predict pQCT measures of tibial geometry and mineralisation at 6-7years.

Year: 2015

Moon RJ, Cole ZA, Crozier SR, Curtis EM, Davies JH, Gregson CL, Robinson SM, Dennison EM, Godfrey KM, Inskip HM, Cooper C, Harvey NC
MRC 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.


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 6-7years of age by dual-energy x-ray absorptiometry (DXA). At 6-7years, 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 (DeltaLM) or FM (DeltaFM) was represented by change in z-score from birth to 7years old and conditioned on the birth measurement. Linear regression was used to explore the associations between DeltaLM or DeltaFM and standardised pQCT outcomes, before and after mutual adjustment and for linear growth. The beta-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 6-7years, were available for 200 children (48.5% male). DeltaLM adjusted for DeltaFM was positively associated with tibial total CSA at both the 4% (beta=0.57SD/SD, p<0.001) and 38% sites (beta=0.53SD/SD, p<0.001), cortical CSA (beta=0.48SD/SD, p<0.001) and trabecular vBMD (beta=0.30SD/SD, p<0.001), but not with cortical vBMD. These relationships persisted after adjustment for linear growth. In contrast, DeltaFM adjusted for DeltaLM 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 6-7years 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.

GID: 3852; Last update: 08.04.2015