Genetic determination and correlation of body mass index and bone mineral density at the spine and hip in Chinese Han ethnicity

The purpose of the present study was to evaluate the magnitude of genetic determination of spine and hip bone mineral density (BMD) and body mass index (BMI), and to explore the genetic, environmental, and phenotypic correlations among the above phenotypes in Chinese Han ethnicity. The sample was composed of at least 217 complete nuclear families in Chinese Han ethnicity. BMD at the spine and hip was measured using a dual-energy X-ray absorptiometry scanner. The heritability ( h (2)) of BMI and BMD at the spine and hip, the genetic correlation (rho(G)) and environmental correlation (rho(E)) among the three phenotypes were evaluated via variance analysis, with age, sex, and age-by-sex interaction as covariates. The phenotypic correlation (rho(P)) and the bivariate heritability rho G(2) were also calculated. The heritability for BMD and BMI was similar to 0.70 and similar to 0.50, respectively ( p< 0.0001). The common environment shared by household members ( household effect) is significant for BMI variation ( p= 0.0004). Significant genetic, environmental, and phenotypic correlation was observed. The rho G(2) values were 0.13 for BMI/ spine BMD, 0.18 for BMI/ hip BMD, and 0.58 for the spine BMD/ hip BMD. While BMD at the spine and hip have significant genetic determination, BMI is more likely to be affected by environmental factors than BMD. In addition, BMD at the spine and hip shares more genetic effect ( pleiotropy) than BMI and BMD do in Chinese Han ethnicity, though the effects are significant for both.