GFAP and Alzheimer disease: In contrast to chronological age's association with classic neurodegenerative markers (Figure 4A and Table S1), whereby higher plasma Aβ40, GFAP, and NfL levels were associated with an older biological age, the top association with age acceleration was with the AD‐specific marker, P‐tau217 (Figure 4B and Table S7), whereby higher P‐tau217 levels were associated with a faster biological age acceleration.