Significant differences in CSF YKL-40 levels were observed in AD vs. HC (SMD = 1.37, 95%CI: [1.09, 1.65]; <i>p</i> = 0.000), MCI vs. HC (SMD = 0.96, 95%CI: [0.51, 1.41]; <i>p</i> = 0.000), and pre-AD vs. HC (SMD = 0.81, 95%CI: [0.39, 1.22]; <i>p</i> = 0.001) comparisons. Here, CHI3L1 is linked to Alzheimer disease.