There was a pattern for a relationship between the Aβ peptides and YKL-40 in younger controls and early-onset AD, but correlation coefficients were low (all r = 0.33–0.44, p < 0.05 except for Aβ43 and YKL-40 in early-onset AD, p = 0.003). Here, CHI3L1 is linked to Alzheimer disease.