Genetic determination and correlation of body weight and body mass index (BMI) and cross-sectional geometric parameters of the femoral neck

Introduction: This study aimed to examine the genetic determination of body weight, body mass index (BMI) and cross-sectional geometric parameters of the femoral neck including cross-sectional area (CSA), cortical thickness (CT), sectional modulus (Z), and buckling ratio (BR), and to test the genetic correlation between body weight/BMI and the femoral neck geometric parameters. Methods A total of 929 healthy subjects from 292 Chinese nuclear families was included. Femoral neck geometric parameters were estimated from bone mineral density (BMD) and bone area which were measured by dual energy X-ray absorptiometry (DXA). Results The heritability (h(2)) estimate values were 0.643, 0.626, 0.626, 0.674, 0.405, and 0.615 for body weight, BMI, CSA, CT, Z, and BR, respectively. Body weight was significantly correlated with bone geometric parameters (p <= 0.001) with genetic correlation (rho(G)) values of 0.551, 0.457, 0.571, and -0.385, and bivariate heritability (rho(2)(G)) values of 0.304, 0.209, 0.326, and 0.148 for CSA, CT, Z, and BR, respectively. Similar correlations (p <= 0.001) were observed between BMI and bone geometric parameters, with rho (G) values of 0.446, 0.432, 0.334, and -0.362, and rho(2)(G) values of 0.199, 0.187, 0.112, and 0.131 for CSA, CT, Z, and BR, respectively. Conclusion In summary, our study suggested that body weight, BMI, and femoral neck geometry were under strong genetic determination. The strong genetic correlations suggested that the genetic factors of bone geometry may be overlapped with those of body weight and BMI.