CHI3L1 and Alzheimer disease: Peripheral blood YKL-40 levels also demonstrated statistically significant elevations in both AD vs. HC (SMD = 0.40, 95%CI: [0.18, 0.63]; <i>p</i> = 0.000) and MCI vs. HC (SMD = 0.79, 95%CI: [0.03, 1.55]; <i>p</i> = 0.043) comparisons.