A blood test can identify two molecules and potentially predict Alzheimer's later in life, a "game-changing" study has found.
The study, published on Monday, has looked into two protein molecules in the blood which contribute to damage in the brain.
Swedish researchers examined 573 patients in their 60s and 70s with mild cognitive impairment (MCI).
It found that the two molecules - P-tau181 and NfL - were the most accurate predictors of the patent's progression from MCI to severe memory and thinking problems - typical of Alzheimer's.
Researchers say blood tests can detect the levels of the two molecules, used to track the progression of Alzheimer's disease in MCI patients.
Musaid Husain, Professor of neurology at the University of Oxford, hailed the research as a "potential gamechanger".
"For the first time, we have a blood test that can predict well the risk of subsequent development of Alzheimer's disease in people who have mild cognitive symptoms," Husain said.
Globally, about 50 million people live with dementia, according to the study.
"Fifty to 70 percent of all dementia cases are caused by Alzheimer's disease," the study says.
"Accurate prognosis is important in MCI, since it may either lead to cognitive decline and dementia.
"If disease-modifying treatments became available for Alzheimer's, accurate prognostics may be important to guide treatment in patients with MCI."
The study was published in the journal Nature Aging.