MAPT and Cognitive impairment: Significant positive correlations were observed between the brain age gap and global tau protein accumulation levels for mild cognitive impairment (<i>r</i> = 0.726, <i>p</i> < 0.001), AD (<i>r</i> = 0.845, <i>p</i> < 0.001), and AD continuum (<i>r</i> = 0.797, <i>p</i> < 0.001).