title: [Study of twin-birth on genetic or environmental determinants of male Chinese smoking initiation].
abstract: OBJECTIVE
  To determine the role of genetic and environmental factors in the onset of smoking in Chinese male twins.
  
  
  METHODS
  Retrospective data on initiation and age at onset of smoking, reported by 1,006 adult twin pairs [aged 18 year-old or more, 638 pairs of monozygotic (MZ) twins and 368 pairs of dizygotic (DZ) twins] were analyzed to calculate the heritability of smoking behavior and smoking initiation.
  
  
  RESULTS
  Different from western culture, 66.8% of males in this Chinese sample are smokers or have the experience of smoking, but only 0.2% of females do so. In the MZ twins, 88.7% (566/638 pairs) of them are both smokers or have smoking experience or both non-smokers, while the number is 63.6% (234/368 pairs) in the DZ twins. The heritability of smoking in this Chinese twin sample is 69.0%+/-4.1%. The smokers usually started their smoking at the age of 20.4+/-5.3 years old. The correlation coefficient for age at onset of smoking in male MZ twin smokers is 0.393, compared to correlation coefficient 0.860 in male DZ twin smokers.
  
  
  CONCLUSIONS
  The moderate level of heritability shows that genetic factors have influence on smoking choice; when the smokers start their smoking, however, this depends more on individual environmental variation in our Chinese twin sample.
authors.affiliation: Department of Epidemiology and Biostatistics, Peking University School of Public Health, Key Laboratory of Epidemiology of Ministry of Education, Peking University, Beijing 100191, China.
authors.forename: Wen-jing
authors.initials: WJ
authors.lastname: Gao
authors.forename: Li-ming
authors.initials: LM
authors.lastname: Li
authors.forename: Wei-hua
authors.initials: WH
authors.lastname: Cao
authors.forename: Si-yan
authors.initials: SY
authors.lastname: Zhan
authors.forename: Jun
authors.initials: J
authors.lastname: Lv
authors.forename: Zeng-chang
authors.initials: ZC
authors.lastname: Pang
authors.forename: Wei-jian
authors.initials: WJ
authors.lastname: Chen
authors.forename: Shao-jie
authors.initials: SJ
authors.lastname: Wang
authors.forename: Rong-fu
authors.initials: RF
authors.lastname: Chen
authors.forename: Yong-hua
authors.initials: YH
authors.lastname: Hu
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002681:China / Q000453:epidemiology; D004200:Diseases in Twins / Q000235:genetics* / Q000523:psychology; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D040582:Inheritance Patterns; D008297:Male; D008875:Middle Aged; D009042:Motivation; D015995:Prevalence; D012189:Retrospective Studies; D012907:Smoking / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology*; D011795:Surveys and Questionnaires; D055815:Young Adult