title: [The importance of memory bias in obtaining age of menarche by recall method in Brazilian adolescents].
abstract: OBJECTIVE
  To compare the age at menarche obtained by recall method according to the time elapsed since the event, in order to verify the importance of the recall bias.
  
  
  METHODS
  Were evaluated 1,671 girls (7-18 years) at schools in Campinas-SP regarding the occurrence of menarche by the status quo method (menarche: yes or no) and the recall method (date of menarche, for those who mentioned it). The age at menarche obtained by the status quo method was calculated by logit, which considers the whole group, and the age obtained by the recall method was calculated as the average of the mentioned age at menarche. In this group, the age at menarche was obtained by the difference between the date of the event and the date of birth. Girls who reported menarche (883, 52.8%) were divided into four groups according to the time elapsed since the event. To analyze the results, we used ANOVA and logistic regression for the analysis, with a significance level of 0.05.
  
  
  RESULTS
  The age at menarche calculated by logit was 12.14 y/o (95% CI 12.08 to 12.20). Mean ages obtained by recall were: for those who experienced menarche within the previous year 12.26 y/o (±1.14), between > 1-2 years before, 12.29 y (±1.22); between > 2-3 years before, 12.23 y/o (±1.27); and more than 3 years before, 11.55y/o (±1.24), p < 0.001.
  
  
  CONCLUSIONS
  The age at menarche obtained by the recall method was similar for girls who menstruated within the previous 3 years (and approaches the age calculated by logit); when more than 3 years have passed, the recall bias was significant.
authors.affiliation: Departamento de Pediatria, Faculdade de Medicina, Pontifícia Universidade Católica de Campinas.
authors.forename: Silvia Diez
authors.initials: SD
authors.lastname: Castilho
authors.affiliation: Faculdade de Medicina, PUC-Campinas.
authors.forename: Luciana Bertoldi
authors.initials: LB
authors.lastname: Nucci
authors.affiliation: Faculdade de Medicina, PUC-Campinas, Campinas, SP, Brasil.
authors.forename: Samanta Ramos
authors.initials: SR
authors.lastname: Assuino
authors.affiliation: Faculdade de Medicina, PUC-Campinas, Campinas, SP, Brasil.
authors.forename: Lucca Ortolan
authors.initials: LO
authors.lastname: Hansen
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D001938:Brazil; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008572:Menarche; D011939:Mental Recall; D012044:Regression Analysis; D013997:Time Factors