A blood test could detect indicators of Alzheimer’s disease many years prior to the onset of symptoms, according to a study in The Lancet. Elevated levels of biomarkers such as tau proteins were linked to poorer cognitive performance and faster decline. Alzheimer’s progressively impairs memory and thinking, eventually disrupting everyday activities. It starts with buildup of amyloid-beta plaques and phosphorylated tau tangles in the brain. While amyloid and tau proteins support normal function, their accumulation can become harmful and lead to neuron loss. Scientists, including researchers from the University of California San Francisco, noted that measuring amyloid-beta and tau levels in blood now serves as a method to monitor protein changes and aid diagnosis. The study assessed biomarker levels including Aβ42, Aβ40, and p-tau217 in blood samples from 1,350 dementia-free adults in the US, averaging 61 years old. Standard high thresholds for amyloid and tau linked to Alzheimer’s appeared in six percent of participants. These elevated levels correlated with weaker midlife performance in cognitive processing speed and executive function, which involves planning, attention, and adapting to change. Participants with high biomarker levels also showed quicker decline on verbal memory and processing speed tests conducted five years apart. The results highlight the promise of blood tests for spotting early Alzheimer’s in middle-aged adults. Early detection could allow reduction of modifiable risks like inactivity, smoking, poor sleep, and untreated hearing loss, plus medication use to potentially slow cognitive decline. The study appeared alongside two other papers in a special Lancet issue on neurology. In an accompanying comment, researchers from Karolinska Institutet cautioned that such blood tests may produce more false positives in younger people without cognitive issues. They recommended using additional diagnostic standards with the tests and noted the biomarkers are unsuitable for broad, untargeted screening in unaffected populations.
