2026-03-11 13:04:00
A simple blood test could predict a woman’s risk of dementia – up to 25 years before symptoms appear.
Scientists believe the breakthrough could transform how the degenerative condition – which causes a decline in thinking, memory, and reasoning skills – is detected and treated.
It could allow doctors to monitor people decades before memory problems begin.
The study, led by scientists at University of California San Diego, found that high levels of a specific protein in the blood were strongly linked to future cognitive decline.
The protein, called p-tau217, is associated with the brain changes seen in Alzheimer’s disease – the most common form of dementia, responsible for around 60 to 70 per cent of cases.
Over time, the disease causes sticky clumps and twisted fibres to build up in the brain, damaging nerve cells and disrupting the signals they use to communicate.
Scientists analysed blood samples from 2,766 women aged between 65 and 79 who were taking part in the long-running Women’s Health Initiative Memory Study.
All were cognitively healthy when the research began.
Over a 25-year follow-up period, researchers tracked who developed mild cognitive impairment – an early stage of memory problems – or dementia.
Women with higher levels of the p-tau217 protein at the start of the study were around three times more likely to develop dementia later in life.
Lead author Professor Aladdin Shadyab said: “That kind of long lead time opens the door to earlier prevention strategies and more targeted monitoring, rather than waiting until memory problems are already affecting daily life.
“Ultimately, the goal is not just prediction, but using that knowledge to delay or prevent dementia altogether.”
The findings, published in JAMA Network Open, also revealed that risk varied between different groups of women.
Those aged 70 or older when the study began showed stronger links between high protein levels and cognitive decline.
The association was also stronger in women carrying the APOE-E4 gene, which is known to increase the risk of Alzheimer’s.
Women using hormone replacement therapy for menopause symptoms were also more likely to develop dementia if they had high levels of the protein.
Experts have welcomed the findings but say more research is needed.
Tara Spires-Jones, from the University of Edinburgh, said: “This is a well conducted observational study showing that race, older age and use of hormone replacement therapy can all affect how effective a blood test is at predicting cognitive decline and dementia in women.”
Michelle Dyson, chief executive of Alzheimer’s Society, added: “Blood tests could transform how dementia is diagnosed… but more research is needed to understand whether early identification of biomarkers can affect whether people will go on to develop dementia later on.”
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