Association of interleukin-6 with sarcopenia and its components in older adults: a systematic review and meta-analysis of cross-sectional studies.

Background: Observational studies have documented increased serum IL-6 levels in elderly individuals afflicted with sarcopenia. Nevertheless, the relationship between serum IL-6 concentrations and sarcopenia prevalence in the aging population is yet to be defined.

Methods: We executed a systematic review and meta-analysis of cross-sectional studies that scrutinized serum IL-6 levels in older adults with and without sarcopenia. Relevant studies were sourced from PubMed, Scopus, Embase, Cochrane Library, and Web of Science from inception until 10 September 2023. The standard mean differences (SMDs) in serum IL-6 levels between studies were synthesized using a random-effects model. To examine the influence of demographic and clinical factors on these outcomes, we performed subgroup analyses and meta-regression, focusing on variables such as sex, age, and body mass index (BMI). We also assessed the relationship between serum IL-6 levels and the defining components of sarcopenia: muscle mass, muscle strength, and physical performance. We used Fisher's Z transformation to standardize the interpretation of effect sizes from these relationships. The transformed values were then converted to summary correlation coefficients (r) for a clear and unified summary of the results.

Results: We included twenty-one cross-sectional studies involving 3,902 participants. Meta-analysis revealed significantly elevated serum IL-6 levels in older adults with sarcopenia compared with those without sarcopenia (SMD = 0.31; 95% CI 0.18, 0.44). The difference was highly pronounced in the subgroups of male and those with female percentage below 50% or a mean BMI below 24 kg/m². Serum IL-6 levels were inversely correlated with muscle mass (summary r = -0.18; 95% CI -0.30, -0.06), but not with handgrip strength (summary r = -0.10; 95%CI: -0.25, 0.05) or gait speed (summary r = -0.09; 95%CI: -0.24, 0.07).

Conclusions: This meta-analysis establishes a link between increased serum IL-6 levels and sarcopenia in the elderly, particularly in relation to decreased muscle mass.