[Genetic effects on physical growth items of child twins in Han nationality]

To analyse the heritabilities of physical growth items of body and its related factors.

An 116 twin pairs of Han nationality, 67 monozygotic (MZ) and 49 like-sex dizygotic (DZ) aged 6 to 12 years, were investigated from June to October in 2004. The measurements included height, weight, sitting height, chest circumference, biacromial breadth and biiliac breadth, and BMI index calculated by the former two measurements. The heritabilities were estimated by using intraclass correlation coefficient method from the adjusted data for age.

The intraclass correlation coefficient was greater in the MZ twins than in the DZ twins. The estimated heritabilities of height, weight, BMI, sitting height, chest circumference, biacromial breadth and biiliac breadth were 0.89, 0.88, 0.73, 0.87, 0.78, 0.78, 0.73 in boys and 0.87, 0.74, 0.72, 0.86, 0.62, 0.56, 0.59 in girls adjusted for age. Therefore, there were no sex difference for the heritabilities of height, sitting height and BMI, but the male heritabilities of weight, chest circumference, biacromial breadth and biiliac breadth were higher than the female's respectively.

Physical growth items should be mainly determined by the genetic factors. There are sex differences for the heritabilities of weight, chest circumference, biacromial breadth and biiliac breadth, i.e., the girls might be affected more easily by environmental factors than the boys in these items.