MAPT and Mental deterioration: We found significant associations between global tau-PET SUVRs and cognitive decline across diagnostic groups within CN (MMSE: β =  − 0.100, T =  − 2.199, p = 0.029, partial R2 = 0.021; ADAS13: β = 0.186, T = 2.984, p = 0.003, partial R2 = 0.037; but not ADNI-MEM [p > 0.05]), MCI (MMSE: β =  − 0.192, T =  − 3.391, p < 0.001, partial R2 = 0.091; ADAS13: β = 0.207, T = 2.274, p = 0.025, partial R2 = 0.044; ADNI-MEM: β =  − 0.112, T =  − 2.028, p = 0.045, partial R2 = 0.035), and dementia (ADNI-MEM: β =  − 0.430, T =  − 2.871, p = 0.008, partial R2 = 0.227; but not MMSE and ADAS [p > 0.05]).