AD-signature cortical thickness [17] was negatively associated with four proteins in CSF, including MMP-10 and YKL-40 (q < 0.05), both of which were differentially regulated in the cross-sectional analyses, and two proteins in plasma, including elafin and lymphotoxin-beta receptor (q < 0.01; Additional file 1: Table S9). Here, CHI3L1 is linked to Alzheimer disease.