Obesity and Smoking are causal factors for meniscal injury: A mendelian randomization study

Abstract Background Previous observational studies have indicated a potential link between obesity, smoking, and meniscal injury. However, it is important to note that these studies are vulnerable to reverse causation and residual confounding. Therefore, the purpose of this study was to examine the causal estimates regarding the impact of these risk factors on meniscal injury. Methods In this study, single nucleotide polymorphisms associated with obesity and smoking were extracted as instrumental variables from the Gene-Wide Association Study database (GWAS). Data on genetic variants of meniscal injuries were obtained from the Finnish database. Heterogeneity of the data was assessed using IVW, MR-Egger and Cochran's Q statistics. Potential causality was assessed using inverse variance weighting, Mendelian randomisation Egger, and weighted median methods. Results Our study showed that obesity and smoking were causal factors for meniscal injuries. (Waist circumference: IVW: OR = 1.59; 95%CI = 1.41–1.80; P<0.001. Hip circumference: IVW: OR = 1.37; 95%CI = 1.23–1.53; P<0.001. BMI: IVW: OR = 1.53; 95%CI = 1.39–1.68; P<0.001. Smoking initiation: IVW: OR = 1.17; 95%CI = 1.00-1.37; P = 0.04. Current smoking: IVW: OR = 2.35; 95%CI = 1.18–4.66; P = 0.01. Past smoking: IVW: OR = 0.75; 95%CI = 0.62–0.90; P<0.01). Conclusion Our results enriched findings from previous epidemiology studies and provided evidence from MR that obesity and smoking have a clear causal effect on meniscal injuries.