Menstrual and reproductive factors and gastric-cancer risk in women.

To understand possible correlates of the systematically higher gastric-cancer rates in males than in females, we investigated the role of menstrual, reproductive and hormonal factors in females, using data from a case-control study conducted in Northern Italy. Cases were 229 post-menopausal women with incident, histologically confirmed gastric cancer, and controls were 614 post-menopausal women in hospital for acute, non-neoplastic, non-digestive-tract conditions. After allowance for age, education, family history, and selected dietary correlates of stomach cancer, a reduced gastric-cancer risk was observed in women with later menopause (odds ratio, OR = 0.6, p value for trend < 0.05), and longer duration of fertile life (OR = 0.7, but the trend in risk was not significant). The risk of gastric cancer was elevated in multiparous women (OR = 1.7 for 3 and 1.9 for > or = 4 births as compared to nulliparae). No association was observed with age at menarche, age at first birth, and with number of spontaneous or induced abortions. Ever-users of oral contraceptives had a non-significant increased risk (OR = 1.3), and users of oestrogen-replacement treatment a non-significant reduced risk (OR = 0.5). Although the association with each factor was moderate, and the interpretation of these findings is not straightforward, these results are compatible with the hypothesis that some role is played by (endogenous and exogenous) female hormones in the process of gastric carcinogenesis.