Images of the brain can help predict whether a person will develop dementia within the next three years before symptoms of the disorder appear, the researchers found.
In one study, researchers at the University of Washington and the University of California, San Francisco, in the United States, used magnetic resonance imaging (MRI) to predict dementia with 89% accuracy.
The results suggest that doctors may someday use widely available tests to inform people about the risk of developing dementia before symptoms appear.
"At the moment, it is difficult to say whether an older person with normal cognition or mild cognitive impairment will likely develop dementia," said Cyrus A Raji, an assistant professor at the University of Washington.
"We showed that a single MRI can predict dementia on average 2.6 years before the memory loss is clinically detectable, which could help doctors advise and care for their patients," Raji said.
Although drugs are not yet available to prevent or delay the onset of Alzheimer's disease, identifying those at high risk for developing dementia in the years to come may still be beneficial, the researchers said.
People can make decisions about their financial and living arrangements while still in full control of their colleges.
Researchers have examined magnetic resonance imaging (MRI) for physical signs of imminent cognitive decline.
They used a technique called diffusion tensor imaging to assess the health of the brain's white matter, which encompasses the cords that allow different parts of the brain to talk to each other.
"The diffusion tensor image is a way of measuring the movement of water molecules along the white matter tracings," Raji said.
"If water molecules are not moving normally, this suggests underlying damage in white deals that may be behind the problems of cognition," he said.
Using information from the Alzheimer's Disease Neuroimaging Initiative – a multi-site collaboration that brings together data, funding and experience to improve clinical trials of Alzheimer's disease – the researchers identified 10 people whose cognitive abilities decreased over a two-year period and compared them to age and sex with 10 people whose thinking skills remained stable.
The mean age of the subjects in both groups was 73. The researchers then analyzed MRI images of the diffusion tensor taken before the 2-year period for all 20 people.
The researchers found that people who went on to experience cognitive decline had significantly more signs of damage to their white matter.
The researchers repeated their analysis in a separate sample of 61 people, using a more refined measure of whiteness.
With this new analysis, they were able to predict cognitive decline with 89% accuracy when analyzing the entire brain. When researchers focused on specific parts of the brain that were more likely to be damaged, accuracy rose to 95 percent.
"We could say that individuals who have developed dementia have these differences in magnetic resonance diffusion compared to the examinations of cognitively normal people whose memory and thinking abilities have remained intact," said Raji.