Aim: To examine the association between parity and gastric cancer (the cases are almost all premenopausal women) risk in a cohort of young parous women.
Methods: The study cohort consisted of all women with a record of a first and singleton childbirth in the Birth Register between 1978 and 1987. We tracked each woman from the time of her first childbirth to December 31, 2008. Their vital status was ascertained by linking records to the computerized mortality database. Cox proportional hazard regression models were used to estimate hazard ratios of death from gastric cancer associated with parity.
Results: There were 1090 gastric cancer deaths (85.87% of them were premenopausal) during 33 686 828 person-years of follow-up. The mortality rate of gastric cancer was 3.24 cases per 100,000 person-years. A trend of increasing risk of gastric cancer was seen with increasing parity. The adjusted hazard ratio was 1.24 [confidence interval (95% CI): 1.02-1.50] for women who had borne two to three children, and 1.32 (95% CI: 1.01-1.72) for women with four or more births, when compared with women who had given birth to only one child.
Conclusion: These results suggest that higher parity may increase the risk of death from gastric cancer among premenopausal women.
Keywords: Cohort study; Gastric cancer; Mortality; Parity.