title: Gene, environment and cognitive function: a Chinese twin ageing study.
abstract: BACKGROUND
  the genetic and environmental contributions to cognitive function in the old people have been well addressed for the Western populations using twin modelling showing moderate to high heritability. No similar study has been conducted in the world largest and rapidly ageing Chinese population living under distinct environmental condition as the Western populations.
  
  
  OBJECTIVE
  this study aims to explore the genetic and environmental impact on normal cognitive ageing in the Chinese twins.
  
  
  METHODS
  cognitive function was measured on 384 complete twin pairs with median age of 50 years for seven cognitive measurements including visuospatial, linguistic skills, naming, memory, attention, abstraction and orientation abilities. Data were analysed by fitting univariate and bivariate twin models to estimate the genetic and environmental components in the variance and co-variance of the cognitive assessments.
  
  
  RESULTS
  intra-pair correlation on cognitive measurements was low to moderate in monozygotic twins (0.23-0.41, overall 0.42) and low in dizygotic twins (0.05-0.30, overall 0.31) with the former higher than the latter for each item. Estimate for heritability was moderate for overall cognitive function (0.44, 95% CI: 0.34-0.53) and low to moderate for visuospatial, naming, attention and orientation abilities ranging from 0.28 to 0.38. No genetic contribution was estimated to linguistic skill, abstraction and memory which instead were under low to moderate control by shared environmental factors accounting for 23-33% of the total variances. In contrast, all cognitive performances showed moderate to high influences by the unique environmental factors.
  
  
  CONCLUSIONS
  genetic factor and common family environment have a limited contribution to cognitive function in the Chinese adults. Individual unique environment is likely to play a major role in determining the levels of cognitive performance.
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, Jinan, Shandong, China Qingdao Center for Disease Control and Prevention, Qingdao, China.
authors.forename: Chunsheng
authors.initials: C
authors.lastname: Xu
authors.affiliation: Qingdao Center for Disease Control and Prevention, Qingdao, China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Sun
authors.affiliation: Qingdao Center for Disease Control and Prevention, Qingdao, China.
authors.forename: Haiping
authors.initials: H
authors.lastname: Duan
authors.affiliation: Qingdao Center for Disease Control and Prevention, Qingdao, China.
authors.forename: Fuling
authors.initials: F
authors.lastname: Ji
authors.affiliation: Qingdao Center for Disease Control and Prevention, Qingdao, China.
authors.forename: Xiaocao
authors.initials: X
authors.lastname: Tian
authors.affiliation: Qingdao Center for Disease Control and Prevention, Qingdao, China.
authors.forename: Yaoming
authors.initials: Y
authors.lastname: Zhai
authors.affiliation: Qingdao Center for Disease Control and Prevention, Qingdao, China.
authors.forename: Shaojie
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, Jinan, Shandong, China Qingdao Center for Disease Control and Prevention, Qingdao, China.
authors.forename: Zengchang
authors.initials: Z
authors.lastname: Pang
authors.affiliation: Department of Public Health, Qingdao University Medical College, Qingdao, China.
authors.forename: Dongfeng
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, Jinan, Shandong, China.
authors.forename: Zhongtang
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Department of Clinical Genetics, Odense University Hospital, Odense, Denmark.
authors.forename: Shuxia
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Psychology, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Matt Mc
authors.initials: MM
authors.lastname: Gue
authors.affiliation: Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark The Danish Twin Registry and The Danish Aging Research Center, Institute of Public Health, University of Southern Denmark, Odense, Denmark.
authors.forename: Jacob V B
authors.initials: JV
authors.lastname: Hjelmborg
authors.affiliation: Department of Clinical Genetics, Odense University Hospital, Odense, Denmark Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark The Danish Twin Registry and The Danish Aging Research Center, Institute of Public Health, University of Southern Denmark, Odense, Denmark.
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.affiliation: Department of Clinical Genetics, Odense University Hospital, Odense, Denmark Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark The Danish Twin Registry and The Danish Aging Research Center, Institute of Public Health, University of Southern Denmark, Odense, Denmark.
authors.forename: Qihua
authors.initials: Q
authors.lastname: Tan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000235:genetics* / Q000502:physiology / Q000523:psychology; D002681:China / Q000453:epidemiology; D003071:Cognition / Q000502:physiology*; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D014427:Twins / Q000235:genetics / Q000523:psychology / Q000706:statistics & numerical data*; D014429:Twins, Dizygotic / Q000706:statistics & numerical data; D014430:Twins, Monozygotic / Q000706:statistics & numerical data
keywords: Chinese twins; ageing; cognitive function; heritability; older people