CHI3L1 and Alzheimer disease: In a subgroup analysis of patients with a mean age range of 60 to 69 years, it was noted that YKL-40 levels were statistically significantly higher in AD patients than in healthy controls (SMD = 0.527, 95%CI: [0.302, 0.752]; p = 0.000; I2 = 0.0%, p = 0.920).