title: Heritability of cigarette smoking and alcohol use in Chinese male twins: the Qingdao twin registry.
abstract: BACKGROUND
  China has the world's largest concentration of smokers (350 million) and rising alcohol consumption, yet little is known about tobacco and alcohol use aetiology. In 2000, the Chinese National Twin Registry was established to provide a genetically informative resource for investigation of health behaviour including tobacco and alcohol use.
  
  
  METHODS
  Using standard twin methodology, this study aimed to examine the relative contribution of genetic and environmental influences on cigarette smoking and alcohol drinking in a sample of adult Chinese twins (n = 1010 individual twins). More than half of the male twins were smokers (58%), and 32.5% reported alcohol consumption. Among male smokers, 46.4% smoked 20 or more cigarettes per day (heavy smokers) and among drinkers, 32.8% consumed one or more drinks per day. Nearly all female twins were non-smokers (99.2%) and non-drinkers (98.7%); therefore, genetic analysis was limited to male data.
  
  
  RESULTS
  In men, current smoking was significantly heritable [75.1%, 95% confidence interval (CI) 56.7-87.5] with no evidence for a significant contribution of shared environmental effects. Heavy smoking was more strongly influenced by genes (66.2%, 95% CI 0-88.4) than shared environment (8.7%, 95% CI 0-71.0). Similarly, current drinking was more strongly influenced by genetic effects (59.5%, 95% CI 0-87.8) than by shared environmental effects (15.3%, 95% CI 0-72.1). Amount of alcohol consumed was influenced to a similar degree by genetic (42.4%, 95% CI 0-91.8) and shared environmental factors (39.2%, 95% CI 0-82.7).
  
  
  CONCLUSIONS
  These results support findings from twins of Western origin on the aetiology of tobacco and alcohol use and encourage further work in Chinese twins.
authors.affiliation: SRI International, Center for Health Sciences, Menlo Park, CA, USA. christina.lessov-schlaggar@sri.com
authors.forename: Christina N
authors.initials: CN
authors.lastname: Lessov-Schlaggar
authors.forename: Zengchang
authors.initials: Z
authors.lastname: Pang
authors.forename: Gary E
authors.initials: GE
authors.lastname: Swan
authors.forename: Qian
authors.initials: Q
authors.lastname: Guo
authors.forename: Shaojie
authors.initials: S
authors.lastname: Wang
authors.forename: Weihua
authors.initials: W
authors.lastname: Cao
authors.forename: Jennifer B
authors.initials: JB
authors.lastname: Unger
authors.forename: C Anderson
authors.initials: CA
authors.lastname: Johnson
authors.forename: Liming
authors.initials: L
authors.lastname: Lee
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000453:epidemiology / Q000235:genetics*; D002681:China / Q000453:epidemiology; D004781:Environmental Exposure; D004812:Epidemiologic Methods; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D012907:Smoking / Q000453:epidemiology / Q000235:genetics*; D014429:Twins, Dizygotic / Q000523:psychology*; D014430:Twins, Monozygotic / Q000523:psychology*