The major findings of our study were: (1) MCI and AD were both associated with a higher NLR and lower LMR, (2) the NLR, but not the LMR, was significantly associated with higher baseline Aβ on PET and longitudinal change in ADAS, and (3) neither NLR or LMR was associated with tau deposition on PET cross-sectionally or longitudinally. Here, MAPT is linked to Alzheimer disease.