[Causal relationship between obesity and male infertility: A two-sample Mendelian randomization study].

Abstract

Objective: To clarify the causal relationship between obesity and male infertility through Mendelian randomization (MR) study.

Methods: We assessed the causal effect of genetically predicted body mass index (BMI) on the risk of male infertility via a two-sample MR analysis, with the BMIs of 99 998 cases and 12 746 controls as the exposure factor and genetic information on male infertility obtained from a genome-wide association study of 73 479 Europeans. In the univariable MR (UVMR) analysis of the causal relationship, we mainly used inverse variance weighting (IVW), with MR-Egger regression and weighted median filtering as the supplementary methods. Sensitivity analyses including the Cochran's Q test, Egger intercept test, MR-PRESSO, leave-one-out analysis and funnel plot were performed to verify the robustness of the MR results. To evaluate the direct causal effects of BMI on MI risk, multivariable MR (MVMR) was performed.

Results: UVMR indicated a causal relationship between genetically predicted BMI and an increased risk of male infertility (OR: 1.237, 95% CI: 1.090－1.404, P = 0.001). Sensitivity analysis revealed little evidence of bias in the current study (P> 0.05). With such risk factors as type 2 diabetes, alcohol consumption and smoking adjusted, MVMR confirmed a direct causal effect of genetically predicted BMI on the risk of male infertility (P<0.05).

Conclusion: Genetically predicted BMI may be associated with an increased risk of male infertility. Further studies are expected to explore the underlying mechanisms of this association and provide some new strategies for the prevention and treatment of BMI-related male infertility.