Scientists have developed a video game that may help diagnose Alzheimer's disease at an early stage, even before clinical signs appear.

The game, called Sea Hero Quest, is a spatial navigation video game that can be played on cell phones, tablets and virtual reality applications.

It has been played by 4 million people since its development, according to the researchers from the University College London in the Uk and National Center for Scientific Research (CNRS) in France.

Strategies deployed to succeed at the game's different quests represent the equivalent of 10,000 years of data collected in labs using traditional experimentation methods, researchers said.

Researchers compared navigational performance on male and female volunteers of all ages, in both the real and virtual world, in Paris and London.

Their results, published on PLOS ONE, validate the theory that virtual navigation performance is strongly on par with that of the real world.

Once the value of assessing navigational abilities via a video game was established, scientists then compared the results of those who played Sea Hero Quest with those who, while not suffering from dementia, have a greater likelihood of developing Alzheimer's disease since they are are APOE type-4 allele carriers.

The latter, tested in the laboratory, recorded normal scores in their answers to traditional neuropsychological surveys.

However, comparing their performance to Sea Hero Quest players of the same age, gender and country of origin highlighted changes in navigational habits even before clinical Alzheimer's symptoms appear.

The results show for the first time how large-scale digital cognitive testing could hold potential for the early detection of Alzheimer's disease and help in personalised testing processes to diagnose the illness in individuals showing no clinical symptoms, researchers said.