Objective

Gastric cancer (GC) is more common in men than women, but also more common among postmenopausal than premenopausal women. The protective effect of reproductive hormones against GC remains unclear. Therefore, we evaluated the association between menopausal hormone therapy (MHT) and the risk of GC in women.

Methods

We investigated the national cohort data of women aged over 40 years who underwent health checkups by the Korean National Health Insurance Service in 2009. After excluding individuals with missing data and those previously diagnosed with cancer, 1,354,621 postmenopausal women were included and divided into groups according to their MHT history. We followed the study population until 2018 and analyzed the hazard ratios (HR) with 95 % confidence intervals (CIs) for the incidence rate of GC in a multivariate adjusted model.

Results

The number of women with and without a history of MHT was 214,723 (15.9 %) and 1,139,898 (84.1 %), respectively. During the mean 8.32 ± 0.8 years of follow-up, a total of 12,496 GC cases developed in the study population (10,962 MHT non-users; 1534 MHT users). In the adjusted model, MHT was associated with a 12 % decrease in the development of GC relative to non-use of MHT (HR 0.88; 95 % CI 0.83–0.93). Exposure to MHT for >2 years was linked to a reduction in GC risk, particularly when initiated before the age of 50, giving a 45 % risk reduction.

Conclusions

According to our large-scale prospective national cohort study, exogenous MHT is associated with a decreased risk of GC in postmenopausal women.