Daijiworld Media Network – Mumbai

Mumbai, May 30: A blood test may help identify people at risk of developing Alzheimer's disease decades before symptoms become evident, according to a new study published in The Lancet journal.

Researchers found that elevated levels of specific blood biomarkers linked to Alzheimer's disease were associated with poorer cognitive performance and a faster rate of mental decline among middle-aged adults.

Alzheimer's disease is a progressive neurological disorder that affects memory, thinking abilities and daily functioning. The disease is marked by the build-up of amyloid-beta plaques and tau protein tangles in the brain, which can damage and eventually destroy nerve cells.

The study, conducted by researchers including a team from the University of California, San Francisco, analysed blood samples from 1,350 dementia-free adults in the United States with an average age of 61 years. Scientists measured levels of Alzheimer's-related biomarkers known as Aβ42, Aβ40 and p-tau217.

The findings revealed that around six per cent of participants had biomarker levels above the standard thresholds associated with Alzheimer's disease. These individuals performed worse in tests measuring processing speed and executive function, which are responsible for skills such as planning, attention and problem-solving.

Researchers also observed a steeper decline in verbal memory and cognitive processing speed over a five-year period among those with elevated biomarker levels.

The study highlights the potential of blood-based testing as a tool for detecting early-stage Alzheimer's disease before noticeable symptoms develop. Early identification could enable individuals to address risk factors such as smoking, physical inactivity, poor sleep and untreated hearing loss, while allowing doctors to initiate interventions aimed at slowing cognitive decline.

However, experts have urged caution. In an accompanying commentary, researchers from Sweden's Karolinska Institutet noted that blood tests may produce false-positive results, particularly among younger adults with no signs of cognitive impairment. They stressed that such tests should be used alongside other diagnostic methods and are not suitable for large-scale screening of healthy populations.

The research forms part of a special neurology-focused issue of The Lancet, underscoring growing efforts to improve the early detection and management of Alzheimer's disease.