Association of menstrual and reproductive factors with pancreatic cancer risk in women: findings of the Japan Collaborative Cohort Study for Evaluation of Cancer Risk

Background The etiology of pancreatic cancer remains largely unknown. We examined the association of pancreatic cancer deaths with menstrual and reproductive factors in a cohort study involving Japanese women. Methods A total of 63 273 women were followed up for mortality from 1988 to 1999. Information on menstrual and reproductive factors was obtained by a questionnaire survey at baseline. Cox proportional-hazards models were used to estimate the relative risks (RRs) and 95% confidence intervals (CIs) for death from pancreatic cancer in relation to menstrual and reproductive factors. Results During 631 401 person-years of follow-up, 154 women died from pancreatic cancer. Parity was not significantly associated with the risk of death from pancreatic cancer; the RR was 0.80 (95% CI, 0.31–2.11) for women with six or more births compared with women with zero or one birth. We found no significant overall association with other reproductive factors, including pregnancy, age at first birth, and menopause. The risk appeared to increase with increasing age at menarche; the RR was 1.49 (95% CI, 0.95–2.34) for women who had menarche after 16 years of age compared to those who had menarche before they were 15 years old. Conclusions Our prospective data indicate that menstrual and reproductive factors are not associated with the risk of death from pancreatic cancer among Japanese women.