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This study aimed to analyze the relationships between the lean mass index (LMI) and bone outcomes in Chinese children and adolescents using dual-energy X-ray absorptiometry (DXA) and to establish sex-specific reference percentile curves for the assessment of muscle status. A total of 1541 Chinese children and adolescents between the ages of 5 and 19 years were recruited from southern China. Body composition was measured by DXA (Lunar Prodigy) to acquire total body and total body less head (TBLH) measures. LMI was calculated as the LM (kg) divided by the height in meters squared. Strong sex gaps were observed after age 14 in total body LMI and appendicular LMI (p < 0.001). LM and LMI values continued to increase for boys up to age 14 compared to girls who plateaued after age 12. For each sex group, total body bone mineral content (BMC) and TBLH BMC were highly correlated with total body LMI and appendicular LMI (r = 0.856-0.916 in boys, and r = 0.651-0.804 in girls, p < 0.001). The appendicular LMI was more strongly associated with total body BMC and TBLH BMC than was total body LMI. The correlations between the BMC values and the LM measures were stronger than the fat mass results. We also present sex-specific percentile curves for LM-age and LMI-age relationships, which could be useful for identifying the LM deficits in this population. [ABSTRACT FROM AUTHOR]

Measurements of body composition by dual-energy X-ray absorptiometry (DXA) have evident value in evaluating skeletal and muscular status in growing children and adolescents. This study aimed to generate age-related trends for body composition in Chinese children and adolescents, and to establish gender-specific reference percentile curves for the assessment of muscle-bone status. A total of 1541 Chinese children and adolescents aged from 5 to 19 years were recruited from southern China. Bone mineral content (BMC), lean mass (LM) and fat mass (FM) were measured for total body and total body less head (TBLH). After 14 years, total body LM was significantly higher in boys than girls ( p < 0.001). However, total body FM was significantly higher in girls than boys in age groups 13-19 years ( p < 0.01). Both LM and FM were consistent independent predictors of total body and subcranial bone mass in both sexes, even after adjustment for the well-known predictors of BMC. The results of multiple linear regression identified LM as the stronger predictor of total body and subcranial skeleton BMC while the fat mass contributed less. For all the subjects, significant positive correlations were observed between total body LM, height, total body BMC and subcranial BMC ( p < 0.01). Subcranial BMC had a better correlation with LM than total body BMC. We have also presented gender-specific percentile curves for LM-for-height and BMC-for-LM which could be used to evaluate and follow various pediatric disorders with skeletal manifestations in this population. [ABSTRACT FROM AUTHOR]