title: Reproductive and menstrual factors and thyroid cancer among Japanese women: the Japan Collaborative Cohort Study.
abstract: OBJECTIVE
  Thyroid cancer is more frequent in women than in men, suggesting the potential role of reproductive and menstrual factors in this cancer. To investigate the association with these factors, we examined 37,986 women involved in the Japan Collaborative Cohort (JACC) Study from 1988 to 1997.
  
  
  METHODS
  Reproductive and menstrual factors were assessed with a self-administered questionnaire at baseline. Hazard ratios (HR) and 95% confidence intervals (95% CI) of thyroid cancer incidence were estimated using Cox proportional hazards regression.
  
  
  RESULTS
  Eighty-six new cases of thyroid cancer were recorded during 379,281 person-years of follow-up. Overall incidence rate was 22.7 per 100,000 person-years, with a diagnosed peak of 38.2 per 100,000 at 55-59 years old. Multivariate HRs of 0.56 (95% CI 0.25-1.24) and 0.52 (95% CI 0.24-1.16) were observed for women who had experienced pregnancy or a live birth, respectively, but without statistical significance. Further, we saw no associations with other factors, such as age at menarche, age at menopause, age at first birth, or hormone use.
  
  
  CONCLUSIONS
  There was no significant association between thyroid cancer and reproductive and menstrual factors in the present study. Additional cohort studies should further examine this possible relationship among Japanese women.
authors.affiliation: Department of Preventive Medicine and Community Health, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan. ptrminh@med.uoeh-u.ac.jp
authors.forename: Truong-Minh
authors.initials: TM
authors.lastname: Pham
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Fujino
authors.forename: Haruo
authors.initials: H
authors.lastname: Mikami
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Okamoto
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Hoshiyama
authors.forename: Akiko
authors.initials: A
authors.lastname: Tamakoshi
authors.forename: Shinya
authors.initials: S
authors.lastname: Matsuda
authors.forename: Takesumi
authors.initials: T
authors.lastname: Yoshimura
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D006304:Health Status; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008019:Life Style; D008572:Menarche; D008875:Middle Aged; D016017:Odds Ratio; D017584:Reproductive History; D012189:Retrospective Studies; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000453:epidemiology*; D016387:Women's Health