Age and sex effects on the relationship between body composition and hip geometric structure in males and females from East China

The study finds bone mineral density is the principal determinant of hip geometry and lean mass is a better determinant than fat mass in Chinese. Moreover, the impact of fat on skeleton differs with age, with a negative effect in young people but a more positive effect in elderly. Purpose The aim of this study was to examine whether the correlation between body composition including bone mineral density (BMD), lean mass (LM) and fat mass (FM), and hip geometric structure change with aging in males and females from East China. Methods It was a cross-section study. A total of 1168 healthy male and 1066 healthy females in Shanghai were divided into six groups based on their age and sex. All participants were evaluated by assessing the BMD of lumber spine and proximal hip, total LM, total FM, and geometric parameters of the hip such as the cross-sectional area (CSA), average cortical thickness (ACT), and the buckling ratio (BR) at the narrow neck (NN), the intertrochanter (IT), and the shaft (FS). Results Among the three body composition, the correlation between hip BMD and hip geometric structure was strongest. LM showed significantly positive correlations with CSA. FM showed negative or little positive correlation with hip geometry in the young group. However, the degree of the contribution of FM to hip geometric structure became substantially positive with aging. Limb LM produced the largest positive contribution to CSA and ACT at all three regions in young males. However, in older males the trunk LM produced the largest positive contribution to CSA and ACT. Conclusions Among all body composition parameters, hip BMD showed the largest correlation with hip geometric structure, with LM showing the second largest. The impact of FM and LM on hip geometry changed with aging and with different