The causal relationship between breast cancer and frozen shoulder: A two-sample Mendelian randomization

To investigate the causal relationship between breast cancer and frozen shoulder using a Mendelian randomization (MR) approach. Pooled data from a large-scale genome-wide association study were used. Genetic loci that were independent of each other and associated with breast cancer and frozen shoulder in populations of European ancestry were selected as instrumental variables. Inverse variance weighting was used as the primary analysis method. Weighted median (WME) and MR-Egger were used as complementary analysis methods to assess causal effects. To explore the causal relationship between breast cancer and frozen shoulder. Sensitivity test analysis was performed using heterogeneity test, multiple validity test, and leave-one-out analysis to explore the robustness of the results. Inverse variance weighting results showed an OR (95% CI) of 1.02 (1.00–1.04), P = .048, indicating that breast cancer is a risk factor for a frozen shoulder. And the test revealed no heterogeneity and pleiotropy, and the sensitivity analysis also showed robust results. In this study, genetic data were analyzed and explored using two-sample MR analysis, and the results showed that the incidence of frozen shoulder was higher in breast cancer patients, suggesting that screening for frozen shoulder in breast cancer patients should be increased.