Fig. 6

a, b Linear regression shows a significant correlation between CHI3L1 and C1q protein levels (a), Iba1-ir and CHI3L1-ir cell numbers (b) across NCI, MCI, and mAD. c A significant positive correlation was observed between CHI3L1 and NPTX2 (r = 0.054, p = 0.0003) protein levels across NCI and MCI, whereas a negative correlation was seen between CD44 and CHI3L2 (d, r = − 0.65, p < 0.0001) protein levels across the four clinical groups. In addition, positive correlations were observed between CHI3L1-ir (e, g) and Iba1-ir microglia cell numbers (f, h) with episodic memory (p = 0.003; e, f) and perceptual speed (p = 0.002; g, h) across NCI, MCI, and mAD. Abbreviations: NCI, noncognitive impairment; MCI, mild cognitive impairment; mAD, mild to moderate AD; sAD, severe AD