Reproductive factors are associated with oesophageal cancer risk: results from a meta-analysis of observational studies.

To further evaluate the association between reproductive events and the development of oesophageal cancer, we searched relevant studies using electronic databases (PubMed, ISI Web of Science). Study-specific relative risks with corresponding 95% confidence intervals (CI) in all analyses were used and multiple summary relative risk (SRR) estimates were calculated. We carried out subgroup analyses and used meta-regression techniques to explore potential sources of heterogeneity. Sensitivity analysis was carried out to identify whether pooled results were influenced by individual studies and publication bias was assessed by Begg's funnel plots and the Egger regression asymmetry test. Fourteen studies were eligible for inclusion in the meta-analysis, summarizing a total of 3816 oesophageal cancer cases. We found that age at menopause (SRR=0.70; 95% CI: 0.51-0.95) and hormone replacement therapy (SRR=0.67; 95% CI: 0.56-0.81) had an association with a decreased risk of oesophageal cancer. A similar result was obtained for parity (SRR=0.79; 95% CI: 0.71-0.89) and ever breastfeeding (SRR=0.65; 95% CI: 0.43-0.97). In contrast, postmenopausal status was associated with increased risk (SRR=1.65; 95% CI: 1.28-2.14). No statistically significant link was found with other exposures. Our meta-analysis supports the substantial influence of reproductive factors, which could be causally linked to oesophageal cancer.