title: Genetic analyses of smoking initiation, persistence, quantity, and age-at-onset of regular cigarette use in Brazilian families: the Baependi Heart Study.
abstract: BACKGROUND
  The purpose of this study was to estimate the genetic influences on the initiation of cigarette smoking, the persistence, quantity and age-at-onset of regular cigarette use in Brazilian families.
  
  
  METHODS
  The data set consisted of 1,694 individuals enrolled in the Baependi Heart Study. The heritability and the heterogeneity in genetic and environmental variance components by gender were estimated from variance components approaches, using the SOLAR (Sequential Oligogenic Linkage Analysis Routines) computer package. The mixed-effects Cox model was used for the genetic analysis of the age-at onset of regular cigarette use.
  
  
  RESULTS
  The heritability estimates were high (> 50%) for smoking initiation and were intermediate, ranging from 23.4 to 31.9%, for smoking persistence and quantity. Significant evidence for heterogeneity in variance components by gender was observed for smoking initiation and age-at-onset of regular cigarette use. Genetic factors play an important role in the interindividual variation of these phenotypes in females, while in males there is a predominant environmental component, which could be explained by greater social influences in the initiation of tobacco use.
  
  
  CONCLUSIONS
  Significant heritabilities were observed in smoking phenotypes for both males and females from the Brazilian population. These data add to the literature and are concordant with the notion of significant biological determination in smoking behavior. Samples from the Baependi Heart Study may be valuable for the mapping of genetic loci that modulate this complex biological trait.
authors.affiliation: Laboratory of Genetics and Molecular Cardiology, Heart Institute, Medical School of University of São Paulo, Av, Dr, Enéas de Carvalho Aguiar, 44, São Paulo, SP, 05403-000, Brazil.
authors.forename: Andréa R V R
authors.initials: AR
authors.lastname: Horimoto
authors.forename: Camila M
authors.initials: CM
authors.lastname: Oliveira
authors.forename: Suely R
authors.initials: SR
authors.lastname: Giolo
authors.forename: Júlia P
authors.initials: JP
authors.lastname: Soler
authors.forename: Mariza
authors.initials: M
authors.lastname: de Andrade
authors.forename: José E
authors.initials: JE
authors.lastname: Krieger
authors.forename: Alexandre C
authors.initials: AC
authors.lastname: Pereira
mesh_terms: D017668:Age of Onset; D000704:Analysis of Variance; D001938:Brazil / Q000453:epidemiology; D005260:Female; D006801:Humans; D040582:Inheritance Patterns / Q000235:genetics*; D008297:Male; D015995:Prevalence; D016016:Proportional Hazards Models; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology* / Q000235:genetics*