Noncausal relationship between body weight and breast cancer based on bidirectional Mendelian randomization evidence

Abstract Background Some observational associations between body weight and breast cancer have attracted attention. However, the causal relationship between these 2 factors remains unclear, and more clinical outcomes are needed for its validation. Methods Based on statistical data from a Genome Wide Association Study, we performed a bidirectional Mendelian randomization analysis to assess the bidirectional causal relationship between body weight and breast cancer using 4 methods, with inverse variance weighting as the primary method. To verify the robustness and reliability of the causal relationship, we performed a sensitivity analysis using horizontal pleiotropy, outlier, and one-by-one elimination tests. Results The inverse variance weighting results revealed no significant positive causal relationship between body weight and breast cancer. Similarly, the reverse analysis revealed no causal effect of breast cancer on body weight. Conclusions The relationship between body weight and breast cancer may be attributed to confounding factors.