American scientists have developed a blood test capable of predicting the risk of dementia (decline in cognitive abilities and memory) in women up to 25 years before symptoms appear.

Researchers say this breakthrough could significantly change how the disease is diagnosed and treated.

The study found that high levels of a specific protein—commonly associated with brain changes in Alzheimer’s disease—are strongly linked to the future risk of cognitive decline in otherwise healthy women.

This discovery could enable doctors to identify at-risk women decades before symptoms arise, opening the door to early monitoring and preventive strategies.

At the start of the study, all participating women were cognitively healthy. The lead author of the research team, Professor Alawaldin Shadab from the University of California, San Diego, said that the long timeline allows preventive measures and targeted monitoring to begin much earlier, instead of waiting until memory problems start affecting daily life.

This approach differs significantly from current diagnostic methods, which typically identify dementia only after noticeable memory decline and other symptoms appear.

The findings were published in the medical journal JAMA Network Open.

The study included 2,766 women aged 65 to 79, who were part of the Women’s Health Initiative Memory Study.

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