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11h ago

Blood Tests and New PET Tracer Reveal Early Alzheimer’s Signals in Some Middle‑Aged Adults

The studies show detectable amyloid and tau biology can forecast faster short‑term cognitive decline while further validation is needed before broader screening.

A sign identifying Sandler Neurosciences Center on the UCSF Mission Bay campus, Feb. 10, 2025, in San Francisco.
Nicole Weber, a UCSF phlebotomist, places vials of blood drawn for a study of chemical exposures, comparing women firefighters and women who work in offices, in a specimen bag in Supervisor Katy Tang’s office at City Hall on Tuesday, Oc. 14, 2014, in San Francisco.
MRI of the brain of a patient affected by Alzheimer’s disease, axial cut-away view. 
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Overview

  • The Lancet published linked papers on Thursday reporting that plasma measures of phosphorylated tau and amyloid identified Alzheimer’s‑related signals in about 6% of 1,350 dementia‑free, middle‑aged participants from the CARDIA cohort.
  • Participants who were biomarker‑positive at baseline had lower processing speed and executive function and faced roughly 2.5–4 times higher odds of rapid 5‑year decline in verbal memory and processing speed.
  • A separate head‑to‑head PET study found the newer tracer MK6240 detected substantially more early tau than the standard tracer Flortaucipir, changing who would be classified as tau‑positive on scans.
  • Authors and editorials caution that single timepoint blood measures, low population prevalence, selection effects, and limited long‑term outcomes reduce predictive value in asymptomatic people and do not justify untargeted screening.
  • Regulatory limits and trial needs remain clear: some assays are cleared only for symptomatic patients, MK6240 is not approved for routine clinical use, and coordinated validation efforts such as the Blood Biomarker Challenge are planned to test clinical rollout.