title: Evaluating gene by sex and age interactions on cardiovascular risk factors in Brazilian families.
abstract: BACKGROUND
  In family studies, it is important to evaluate the impact of genes and environmental factors on traits of interest. In particular, the relative influences of both genes and the environment may vary in different strata of the population of interest, such as young and old individuals, or males and females.
  
  
  METHODS
  In this paper, extensions of the variance components model are used to evaluate heterogeneity in the genetic and environmental variance components due to the effects of sex and age (the cutoff between young and old was 43 yrs). The data analyzed were from 81 Brazilian families (1,675 individuals) of the Baependi Family Heart Study.
  
  
  RESULTS
  The models allowing for heterogeneity of variance components by sex suggest that genetic and environmental variances are not different in males and females for diastolic blood pressure, LDL-cholesterol, and HDL-cholesterol, independent of the covariates included in the models. However, for systolic blood pressure, fasting glucose and triglycerides, the evidence for heterogeneity was dependent on the covariates in the model. For instance, in the presence of sex and age covariates, heterogeneity in the genetic variance component was suggested for fasting glucose. But, for systolic blood pressure, there was no evidence of heterogeneity in any of the two variance components. Except for the LDL-cholesterol, models allowing for heterogeneity by age provide evidence of heterogeneity in genetic variance for triglycerides and systolic and diastolic blood pressure. There was evidence of heterogeneity in environmental variance in fasting glucose and HDL-cholesterol.
  
  
  CONCLUSIONS
  Our results suggest that heterogeneity in trait variances should not be ignored in the design and analyses of gene-finding studies involving these traits, as it may generate additional information about gene effects, and allow the investigation of more sophisticated models such as the model including sex-specific oligogenic variance components.
authors.affiliation: Laboratory of Genetics and Molecular Cardiology, Heart Institute, Medical School of University of Sao Paulo, Sao Paulo, Brazil. giolo@ufpr.br
authors.forename: Suely R
authors.initials: SR
authors.lastname: Giolo
authors.forename: Alexandre C
authors.initials: AC
authors.lastname: Pereira
authors.forename: Mariza
authors.initials: M
authors.lastname: de Andrade
authors.forename: José E
authors.initials: JE
authors.lastname: Krieger
authors.forename: Júlia P
authors.initials: JP
authors.lastname: Soler
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil / Q000453:epidemiology; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D005190:Family; D005260:Female; D005796:Genes / Q000502:physiology; D018740:Genetic Heterogeneity; D006801:Humans; D008297:Male; D008875:Middle Aged; D040641:Quantitative Trait Loci; D012307:Risk Factors; D012737:Sex Factors; D055815:Young Adult