Objective: To investigate the varying variances of the genetic components in birth cohorts. Methods: Twin samples used in the current study were collected from the Chinese National Twin Registry and a two-wave study was conducted, in Qingdao and Lishui regions. Samples were broken down by birth cohort to create four subgroups: -1958, 1959-1961, 1962-1970 and 1970-. Structural equation models were fitted in each subgroup to estimate the genetic and environmental variances. Results: From each birth cohort, weight and body mass index in 2012 appeared higher than those in 2001. Twins of 1971- cohort subgroup showed lower weight than in the other cohort subgroups. Except for the 1959-1961 cohort subgroup, the later birth cohorts were inversely related to the body mass indexes. Genetic factors might explain 54%-76% of the total variations on the body mass index. Heritability of body mass index of twins born during 1959-1961 was increasing along with age. Conclusion: Genetic factors might explain the main portion which related to the phenotypic variance of body mass index. Effects of genetic factors on body mass index of twins born during 1959-1961 might have increased along with age.
目的： 探索不同出生队列BMI遗传度的变化情况。 方法： 基于中国双生子登记系统丽水和青岛两个时点的双生子，按照出生年份分为1958年及以前出生、1959－1961年出生、1962－1970年出生和1971年及以后出生的4个出生队列，在各个时点分别拟合结构方程，计算不同出生队列在不同年龄的遗传度。 结果： 每个出生队列中，2012年时的体重、BMI高于2001年；出生于1971年及以后的双生子无论体重和BMI均低于其余出生队列。遗传因素能解释BMI的表型变异为54%~76%；出生于1959－1961年的双生子，BMI的遗传度随年龄上升，其余出生队列遗传度较为稳定。 结论： BMI受遗传因素影响较大，出生于1959－1961年的双生子，随着年龄增长，遗传因素对BMI的影响增加。.
Keywords: Birth cohort; Body mass index; Heritability; Twin study.