Associations were markedly reduced for P-tau181 versus microglia-related proteins (e.g., sTREM2 or TAM receptors [sAXL and sTYRO3]), astrocytic biomarker YKL-40 and the Parkinson’s disease-related biomarker α-synuclein, indicating that these biological processes/pathologies may not be as related to tau-pathology as both we and others have previously suggested20,21,29–31. Here, CHI3L1 is linked to Parkinson disease.