Reproductive factors and risk of oesophageal cancer, a population-based nested case–control study in Sweden

BACKGROUND: The role of sex hormonal influence in explaining the strong male predominance in oesophageal adenocarcinoma (EA) needs attention. METHODS: A nation-wide nested case-control study was initiated from the Swedish Multi-Generation Register with subjects born since 1932. The study exposures were the number of children and age at having the first child. Cases of EA, gastroesophageal junctional adenocarcinoma (EJA), and oesophageal squamous cell carcinoma (SCC) were identified. Ten age- and sex-matched controls were randomly selected for each case. Conditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: In women, 115 EA, 246 EJA, and 363 SCC were identified. Comparing parous with non-parous women, a decreased risk of EA was indicated (OR=0.66, 95% CI 0.38-1.14), which became statistically significant when EA and EJA were combined (OR=0.73, 95% CI 0.53-0.99). All these associations were, however, at least as strong in men. Age at first birth did not show significant risk in women, but showed risk in men. In addition, the results were similar for SCC in both sexes. CONCLUSION: These findings indicate that associations between the reproductive factors parity and age at first birth, and risk of EA might not be explained by sex hormonal influence.