Breastfeeding and subsequent risk of 24 types of maternal cancer: a cohort study of Chinese women

Background Existing epidemiological evidence on breastfeeding and cancer risks is inconsistent, and no studies have thoroughly examined the relationship between breastfeeding and each site-specific cancer in China. We aimed to investigate these associations among parous Chinese women. Methods A total of 157,454 participants aged 40–75 years from 2012 to 2021 were recruited. Cox proportional hazards model was applied to explore the association between breastfeeding behaviors and cancer risks by hazard ratios (HRs) and corresponding 95% confidence intervals (CIs). Results 5,542 incident cancer cases were identified with a median follow-up of 4.81 years. The history of breastfeeding was statistically significantly associated with lower risk of breast cancer in the multivariate-adjusted model (HR = 0.78, 95%CI: 0.65–0.94). In addition, the risk of gallbladder cancer increased with increasing months of total breastfeeding ( P -trend = 0.039), with a 51% increase in risk for each additional 12 months of breastfeeding (HR = 1.51, 95%CI: 1.12–2.02). The risk of breast cancer decreased with increasing months of total breastfeeding ( P -trend = 0.015), with a 15% reduction in risk for each additional 12 months of breastfeeding (HR = 0.85, 95%CI: 0.76–0.95). The subgroup analyses according to menopausal status shows significant separations for colon-rectum cancer, uterus cancer, oesophagus cancer, and larynx cancer (all P -interaction < 0.05). In addition, significant linear associations were suggested concerning gallbladder cancer ( P -overall = 0.0302, P -nonlinear = 0.6558) and breast cancer ( P -overall = 0.0175, P -nonlinear = 0.5544). Conclusions This study provides further support for the role of breastfeeding behavior in overall cancer and its 24 site-specific cancers.