Early tau deposition was elevated in women compared with men in individuals on the Alzheimer disease (AD) trajectory, a recent study found. These findings lend support to a growing body of literature that highlights a biological underpinning for sex differences in AD risk. Researchers conducted a study of 2 cross-sectional, convenience-sampled cohorts of clinically normal individuals who received tau and β-amyloid (Aβ) PET scans. Data were collected between January 2016 and February 2018 from 193 clinically normal individuals from the Harvard Aging Brain Study who underwent carbon 11–labeled Pittsburgh Compound B and flortaucipir F18 PET and 103 clinically normal individuals from the Alzheimer’s Disease Neuroimaging Initiative who underwent florbetapir and flortaucipir F 18 PET. They found:

• The mean (SD) age of all individuals was 74.2 (7.6) years (81 APOE ε4 carriers [31%]; 89 individuals [30%] with high Aβ).
• There was no clear association of sex with regional tau that was replicated across studies.
• However, in both cohorts, clinically normal women exhibited higher entorhinal cortical tau than men, which was associated with individuals with higher Aβ burden.
• A sex by APOE ε4 interaction was not associated with regional tau.