Female reproductive factors, exogenous hormone use, and pancreatic cancer risk: the Japan Public Health Center-based prospective study.

An association between female reproductive factors, exogenous hormone use, and pancreatic cancer risk has long been suggested in laboratory settings, but epidemiological findings remain mixed and inconclusive. Studies carried out on Asian populations are also limited. In this study, 45 617 women aged 40-69 years were followed for an average of 18.4 years in the Japan Public Health Center-based prospective cohort and 211 pancreatic cases were identified as of 31 December 2011. We applied multivariate-adjusted Cox proportional hazards regression models using age as a time-scale to assess the association between female reproductive factors (menstrual status, menarche age, menopause age, number of births, age at first birth, total years of fertility, history of breastfeeding) and exogenous hormone use with the incidence of pancreatic cancer through hazard ratios and confidence intervals. No significant associations were found between our examined female reproductive factors and pancreatic cancer incidence. The use of exogenous hormones was found to be associated with an increased risk of pancreatic cancer in a multivariate-adjusted model (hazard ratio: 1.47; 95%; confidence interval: 1.00-2.14) in the Japanese female population. Our results suggest that exogenous hormones may play a role in the formation of pancreatic cancer, and further prospective studies are warranted for clarification.