Association between sarcopenia and intervertebral disc degeneration: A bidirectional two-sample Mendelian randomization

Background Sarcopenia (SP) and Intervertebral Disc Degeneration (IVDD) are common age-related diseases that significantly affect the physical and mental health of patients. A substantial body of evidence suggests a potential association between SP and IVDD. However, the causal relationship between SP and IVDD remains uncertain. Objectives This study aimed to determine whether the association between SP and IVDD is causal by employing Mendelian randomization (MR) analysis. Methods Genome-wide association study (GWAS) data related to SP (measured by muscle lean mass, left- and right-hand grip strength, and walking speed) and IVDD were obtained from the UK Biobank and FinnGen. To investigate the causal relationship between SP and IVDD, three MR analysis methods were employed, primarily focusing on the Inverse-Variance Weighted (IVW) approach. The robustness of causal effects was ensured through multiple methods: Instrumental Variables (IVs) were evaluated using F-values; heterogeneity was assessed using Cochran's Q; horizontal pleiotropy was evaluated using MR Egger regression; and outliers was detected using MR-PRESSO and the leave-one-out method. Results The analysis indicates a potential causal relationship between appendicular lean mass (ALM) and the risk of IVDD (OR = 0.89, 95% CI: 0.809–0.98; P < 0.05). Similarly, left-hand grip strength shows a potential causal relationship with IVDD risk (OR = 1.52, 95% CI:1.08–2.14; P < 0.05), as does right-hand grip strength (OR = 1.50, 95% CI:1.09–2.07; P < 0.05). Additionally, a potential causal relationship is observed between IVDD and walking speed (OR = 0.99, 95% CI:0.97–1.00; P < 0.05). Conclusion The findings suggest that ALM may serve as a protective factor against IVDD, while left- and right-hand grip strength may be risk factors for the development of IVDD. Furthermore, IVDD appears to be a risk factor associated with reduced walking speed. Further research is necessary to elucidate the underlying mechanisms of these associations.