A virtual reality test has been shown to predict Alzheimer's disease decades before symptoms emerge.

German researchers had people aged 18 to 30 to navigate through a virtual maze to test the function of certain brain cells and found those with a high genetic risk of Alzheimer's could be identified by their performance, BBC News reports.

The findings, published in the journal Science, could help future research, diagnosis and treatment.

"Our results could provide a new basic framework for preclinical research on Alzheimer's disease and may provide a neurocognitive explanation of spatial disorientation in Alzheimer's disease," said the researchers, led by Lukas Kunz of the German Centre for Neurodegenerative Diseases in Bonn.

They added that the high risk group navigated the maze differently because of reduced functioning of a type of brain cell involved in spatial navigation.