title: A prospective study of reproductive and menstrual factors and colon cancer risk in Japanese women: findings from the JACC study.
abstract: The effects of reproductive factors on the etiology of colon cancer in Asian populations remain unexplored. So we examined 38,420 Japanese women aged 40-79 years who responded to a questionnaire on reproductive and other lifestyle factors from 1988 to 1990 in the Japan Collaborative Cohort Study for Evaluation of Cancer Risk. During an average 7.6 years of follow-up, we documented 207 incident colon cancers. Multivariate analysis indicated that colon cancer risk was likely to be lower among parous women than among nulliparous. Women who had two abortions or more had a 72% higher risk of developing colon cancer [relative risk (RR) 1.72; 95% confidence interval (CI) 1.16-2.55; trend P < 0.01] compared with women who never had an abortion. The RR of colon cancer among postmenopausal women significantly decreased with increasing age at menarche (trend P = 0.01). No apparent association between colon cancer and gravida, age at first birth, age at menopause, or duration of menstruation was seen. These prospective data support the hypothesis that female reproductive events modify colon cancer risk, and suggest that reproductive factors, particularly age at menarche and having an abortion, may be of importance in the etiology of colon cancer among Japanese women.
authors.affiliation: Department of Public Health/Health Information Dynamics, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya 466-8550, Japan. tamako@med.nagoya-u.ac.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Tamakoshi
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.forename: Masayo
authors.initials: M
authors.lastname: Kojima
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Norihiko
authors.initials: N
authors.lastname: Hayakawa
authors.forename: Hideaki
authors.initials: H
authors.lastname: Toyoshima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yatsuya
authors.forename: Takaaki
authors.initials: T
authors.lastname: Kondo
authors.forename: Shinkan
authors.initials: S
authors.lastname: Tokudome
authors.forename: Shuji
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Koji
authors.initials: K
authors.lastname: Suzuki
authors.forename: Sadao
authors.initials: S
authors.lastname: Suzuki
authors.forename: Miyuki
authors.initials: M
authors.lastname: Kawado
authors.forename: Kotaro
authors.initials: K
authors.lastname: Ozasa
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ito
authors.forename: Akiko
authors.initials: A
authors.lastname: Tamakoshi
mesh_terms: D000028:Abortion, Induced; D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D000368:Aged; D015331:Cohort Studies; D003110:Colonic Neoplasms / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008019:Life Style; D008572:Menarche; D008598:Menstruation; D008875:Middle Aged; D015999:Multivariate Analysis; D010298:Parity; D017698:Postmenopause; D011446:Prospective Studies; D012307:Risk Factors