Impact of reproductive factors on breast cancer incidence: Pooled analysis of nine cohort studies in Japan.

ABSTRACT: Prior studies reported the association of reproductive factors with breast cancer (BC), but the evidence is inconsistent. We conducted a pooled analysis of nine cohort studies in Japan to evaluate the impact of six reproductive factors (age at menarche/age at first birth/number of births/age at menopause/use of female hormones/breastfeeding) on BC incidence. We conducted analyses according to menopausal status at the baseline or at the diagnosis. Hazard ratio (HR) and 95% confidence interval (CI) were estimated by applying Cox proportional-hazards model in each study. These hazard ratios were integrated using a random-effects model. Among 187,999 women (premenopausal: 61,113, postmenopausal: 126,886), we observed 873 premenopausal and 1,456 postmenopausal cases. Among premenopausal women,

SUBMITTER: Takeuchi T 

PROVIDER: S-EPMC7957169 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature