MAPT and Alzheimer disease: ↓ NAA/Cr in early AD (A+T+N−) and late AD (A+T+N+) compared to controls (A−T−N−; A+T−N−). ↑ mIns/Cr in late AD compared to controls.↓ NAA/Cr correlated with ↑ global Aβ load (PIB) and tau load (flortaucipir) on PET in whole cohort.