Those that played the game at least 10 hours, either at home or in a laboratory, gained on average three years of cognitive improvement when tested after one year, according to a formula developed by the researchers.
A group that got four additional hours of training improved their cognitive abilities by an average of four years. In speed and attention tests their brains were up to seven years younger, it was found.
Lead author Fredric Wolinsky, professor in the University's College of Public Health, said: "We not only prevented the decline; we actually sped them up."
He attributed the benefits to the range of skills required in the game, adding: "We know that we can stop this decline and actually restore cognitive processing speed to people.
"So, if we know that, shouldn't we be helping people? It's fairly easy, and older folks can go get the training game and play it."
The study comes amidst a burst of research examining why, as we age, our minds gradually lose "executive function," generally considered mission control for critical mental activities, such as memory, attention, perception and problem solving.
Studies show loss of executive function occurs as people reach middle age; other studies say our cognitive decline begins as soon as the age of 28.
Either way, our mental capacities do diminish and medical and public health experts are keen to understand why in an effort to stem the inexorable tide as much as possible.
Professor Wolinsky and his colleagues separated 681 generally healthy medical patients into four groups, then further separated them into those 50 to 64 years of age and those over age 65.
One group was given computerised crossword puzzles, while three other groups were exposed to the game Road Tour.
The game involves identifying a type of vehicle and then re-identifying the vehicle type and matching it with a road sign displayed from a circular array of possibilities, all but one of them false icons.
The player must succeed at least three out of every four tries to advance to the next level, which speeds up the vehicle identification and adds more distractions, up to 47 in all.
The goal is to increase the user's mental speed and agility at identifying the vehicle symbol and picking out the road sign from distractors.
Professor Wolinsky said: "The game starts off with an assessment to determine your current speed of processing. Whatever it is, the training can help you get about 70 per cent faster."
The researchers found those who played Road Tour also scored far better than the crossword puzzle group on tests involving executive function.
The game has previously been credited with improving quality of life, easing depression and cutting medical bills.
The findings were published in the journal PLOS One.
However, some were sceptical about the research. Dr Doug Brown, director of research at the Alzheimer’s society, told the Daily Mail: “Many of us enjoy puzzling over a game.
“However, there is currently little evidence that brain training has any cognitive benefits.”
