A simple blood test may soon help identify individuals at higher risk of Alzheimer’s disease years before they show any symptoms, according to a recent study. Researchers from the University of California, San Francisco (UCSF) in the United States have discovered that certain Alzheimer’s-related proteins found in the blood are associated with minor differences in thinking and memory among middle-aged adults who do not yet have dementia.
Alzheimer’s disease is the most common form of dementia, which occurs due to various diseases and injuries that affect the brain. While there are medications available to manage symptoms, there is currently no cure for dementia. The research team highlights that this is the first time such blood markers have been shown to correlate with subtle cognitive changes in this specific group of individuals.
“For some people who discover they have these biomarkers, testing could open a window to engage in interventions that might delay the onset of Alzheimer’s,” said Kristine Yaffe, senior author of the study and vice chair in the Department of Psychiatry and Behavioural Sciences at UCSF.
The study involved testing blood samples from 1,350 adults aged between 53 and 69 for two proteins—amyloid and tau—that are well-known indicators of Alzheimer’s disease. Approximately 6% of participants had high levels of both proteins. Although they did not have dementia, these individuals were slower to respond to changing information, such as traffic signals or conversations, and faced greater challenges with tasks requiring planning, organization, and staying on track, like managing finances or arranging schedules.
When researchers retested the participants five years later, those with high levels of Alzheimer’s-related proteins showed a faster decline in verbal memory and processing speed. This suggests that blood tests could potentially enable earlier and more affordable diagnosis of dementia.
Currently, MRI scans are used to diagnose dementia, but they are costly and not always widely accessible. Patient advocacy groups emphasize that obtaining a clear diagnosis is often difficult and frequently occurs too late, when symptoms are already advanced, leading to significant brain damage.
The findings offer hope that blood tests could eventually help doctors detect Alzheimer’s risk earlier and more efficiently than current methods. However, while medical professionals see potential in this approach as a research tool, they caution that it is not yet suitable for widespread screening.
“The drawback of this kind of test is that it may be misinterpreted as a definitive sign of Alzheimer’s disease, which is not what we are suggesting here,” said Tara Spires-Jones, professor of neurodegeneration at the University of Edinburgh and division lead at the UK Dementia Research Institute. “This test provides a signal of what’s happening, but it’s just one part of the overall picture. It isn’t a diagnosis on its own,” she explained.
These tests are currently approved in the US for individuals who already exhibit symptoms, but they are designed to detect Alzheimer’s specifically, not other types of dementia. Despite this, early detection remains valuable, especially since several risk factors for dementia can be modified. These include physical inactivity, smoking, depression, poor heart health, and low levels of cognitive activity.
According to Yaffe, up to 40% of dementia cases could be delayed or prevented by addressing these modifiable risk factors. In 2021, the World Health Organization reported that 57 million people worldwide had dementia, with nearly 10 million new cases diagnosed each year.
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