Serum levels of CHI3L1 exhibited a reduction in ALS patients when contrasted with individuals with AMDS (ALS-C pooled SMD, − 0.37; 95% CI, − 0.63 to − 0.11; P = 0.552) (Fig. 8), but the difference was not statistically significant, possibly due to the limited inclusion of studies. This evidence concerns the gene CHI3L1 and amyotrophic lateral sclerosis.