In a significant finding, UK researchers have developed a new test that can predict dementia -- affecting over 55 million people worldwide -- nine years before a diagnosis.

The new test is 80 per cent more accurate than the commonly used methods like memory tests or measurements of brain shrinkage, said researchers at the Queen Mary University of London.

The test is based on analyses of functional MRI (fMRI) scans and detects changes in the brain’s ‘default mode network’ (DMN) -- which connects regions of the brain to perform specific cognitive functions.

DMN is the first neural network to be affected by Alzheimer’s Disease. Charles Marshall from Queen Mary’s Wolfson Institute of Population Health called the predictive test “vital for developing treatments that can prevent the irreversible loss of brain cells that causes the symptoms of dementia.”

To estimate the effective connectivity between ten regions of the brain that constitute the default mode network, the team used fMRI scans from over 1,100 volunteers.

The findings, published in the journal Nature Mental Health, showed that the model had accurately predicted the onset of dementia up to nine years before an official diagnosis was made and with greater than 80 per cent accuracy.

In the cases where the volunteers had gone on to develop dementia, it was also found that the model could predict within a two-year margin of error exactly how long it would take that diagnosis to be made.

Further, the researchers found that genetic risk for Alzheimer's was strongly associated with connectivity changes in the DMN. They also found social isolation can affect connectivity in the DMN and raise the risk of dementia.