MAPT and Alzheimer disease: Interestingly, AD groups usually had significantly higher levels of CSF YKL-40 compared to DLB, and in one DLB cohort, CSF YKL-40 levels were positively related to AD-associated tau pathology [64], suggesting that astrocyte activity, or at least expression of this related molecule, may be more relevant to AD neuropathology than α-synucleinopathy.