Menstrual and Reproductive Risk Factors and Risk for Gastric Adenocarcinoma in Women: Findings From the Canadian National Enhanced Cancer Surveillance System

The role of menstrual and reproductive risk factors for gastric cancer has not been well studied. This population-based case–control study included 326 women aged 20 to 74 years with gastric adenocarcinoma. Controls were 326 women frequency matched on age. Data for reproductive and/or hormonal exposure and gastric cancer risk factors were captured through self-administered questionnaire. Later age at menarche was associated with increased risk for adenocarcinoma compared with menarche onset at younger than 13 years of age (13 to 14 years: odds ratio [OR], 1.45; 95% confidence interval [CI], 1.00–2.10; ≥15 years: OR, 1.93; 95% CI, 1.19–3.13). Compared with premenopause, natural menopause was associated with increased risk for adenocarcinoma (OR, 1.99; 95% CI, 0.98–4.05). Compared with nulliparity, 4 or more births were associated with decreased risk for gastric cancer, as was being pregnant for 5 months or longer if the first pregnancy occurred at younger than 24 years (OR, 0.55; 95% CI, 0.31–0.96) or 25 years or older (OR, 0.67; 95% CI, 0.38–1.18). Oral contraceptives and hormone replacement therapy were associated with a non–statistically significant decreased risk. These findings suggest that hormonal factors associated with greater exposure to estrogen and/or progesterone may be associated with decreased risk for gastric cancer.