Reproductive factors, exogenous female hormone use and breast cancer risk in Japanese

The Miyagi Cohort Study

Masaaki Kawai, Yuko Minami, Shinichi Kuriyama, Masako Kakizaki, Yoichiro Kakugawa, Yoshikazu Nishino, Takanori Ishida, Akira Fukao, Ichiro Tsuji, Noriaki Ohuchi

Research output: Contribution to journalArticle

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Abstract

The incidence of breast cancer among Japanese women is substantially increasing. This population-based prospective cohort study in Japan evaluated the associations of reproductive factors and exogenous female hormone use with breast cancer risk, both overall and separately among premenopausal and postmenopausal women. A total of 24,064 women aged 40-64 were followed from 1990 to 2003. During 309,424 person-years of follow-up, 285 breast cancer cases were documented. In overall evaluation, nulliparity was significantly associated with an increased risk of breast cancer. There was a significant decrease in risk with increasing parity number among parous women (trend P = 0.008). No association was observed between age at menarche or age at first birth and breast cancer risk. Neither oral contraceptive (OC) use nor the use of exogenous female hormones other than OC was associated with breast cancer risk. The evaluation according to menopausal status revealed that nulliparity and parity number were significantly related to breast cancer risk only among postmenopausal women. Later age at natural menopause was associated with an increased risk of breast cancer among postmenopausal women (trend P = 0.02). Our findings suggest that parity number and age at menopause have great effects on breast cancer risk among Japanese women.

Original languageEnglish
Pages (from-to)135-145
Number of pages11
JournalCancer Causes and Control
Volume21
Issue number1
DOIs
Publication statusPublished - 01-01-2010

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Cohort Studies
Hormones
Breast Neoplasms
Parity
Oral Contraceptives
Menopause
Menarche
Birth Order
Japan
Prospective Studies
Incidence
Population

All Science Journal Classification (ASJC) codes

  • Oncology
  • Cancer Research

Cite this

Kawai, Masaaki ; Minami, Yuko ; Kuriyama, Shinichi ; Kakizaki, Masako ; Kakugawa, Yoichiro ; Nishino, Yoshikazu ; Ishida, Takanori ; Fukao, Akira ; Tsuji, Ichiro ; Ohuchi, Noriaki. / Reproductive factors, exogenous female hormone use and breast cancer risk in Japanese : The Miyagi Cohort Study. In: Cancer Causes and Control. 2010 ; Vol. 21, No. 1. pp. 135-145.
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Kawai, M, Minami, Y, Kuriyama, S, Kakizaki, M, Kakugawa, Y, Nishino, Y, Ishida, T, Fukao, A, Tsuji, I & Ohuchi, N 2010, 'Reproductive factors, exogenous female hormone use and breast cancer risk in Japanese: The Miyagi Cohort Study', Cancer Causes and Control, vol. 21, no. 1, pp. 135-145. https://doi.org/10.1007/s10552-009-9443-7

Reproductive factors, exogenous female hormone use and breast cancer risk in Japanese : The Miyagi Cohort Study. / Kawai, Masaaki; Minami, Yuko; Kuriyama, Shinichi; Kakizaki, Masako; Kakugawa, Yoichiro; Nishino, Yoshikazu; Ishida, Takanori; Fukao, Akira; Tsuji, Ichiro; Ohuchi, Noriaki.

In: Cancer Causes and Control, Vol. 21, No. 1, 01.01.2010, p. 135-145.

Research output: Contribution to journalArticle

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AU - Ohuchi, Noriaki

PY - 2010/1/1

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N2 - The incidence of breast cancer among Japanese women is substantially increasing. This population-based prospective cohort study in Japan evaluated the associations of reproductive factors and exogenous female hormone use with breast cancer risk, both overall and separately among premenopausal and postmenopausal women. A total of 24,064 women aged 40-64 were followed from 1990 to 2003. During 309,424 person-years of follow-up, 285 breast cancer cases were documented. In overall evaluation, nulliparity was significantly associated with an increased risk of breast cancer. There was a significant decrease in risk with increasing parity number among parous women (trend P = 0.008). No association was observed between age at menarche or age at first birth and breast cancer risk. Neither oral contraceptive (OC) use nor the use of exogenous female hormones other than OC was associated with breast cancer risk. The evaluation according to menopausal status revealed that nulliparity and parity number were significantly related to breast cancer risk only among postmenopausal women. Later age at natural menopause was associated with an increased risk of breast cancer among postmenopausal women (trend P = 0.02). Our findings suggest that parity number and age at menopause have great effects on breast cancer risk among Japanese women.

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