Ken Lehmann is taking his Alzheimer's diagnosis very seriously: He's making a game of it.

Three and a half years ago, the retired furniture executive from Edina learned he was in the early stages of the disease. Since then, the 76-year-old has been following his doctor's advice — by playing brain games on his iPad.

"Knock on wood, I haven't regressed as rapidly as some of my friends," Lehmann said.

The games, which promise to sharpen thinking skills and fight memory loss, are surging in popularity as millions of Americans download the mental workouts. And while scientists and doctors have long debated the value of "brain fitness," many have recommended that older adults work to keep their minds alert, through everyday social interaction or structured gaming.

Now, new research supports the theory that exercising the mind could slow the onset of dementia and increase mental dexterity.

In the largest and longest study of its kind, older adults who completed a series of brain-training exercises maintained their cognitive skills a decade later, while those who received no brain training did not.

"Our findings suggest that if you want to keep your mind stronger as you get older, you can't become a couch potato," said George Rebok, professor at Johns Hopkins University's Bloomberg School of Public Health and lead author of the study.

Rise of brain workouts

For years, puzzles were purported to keep the brain nimble. First it was crossword puzzles. Then Sudoku. Now it's a new generation of apps — such as BrainHQ, Fit Brains Trainer and Lumosity — that claim to target and train specific parts of the brain.

The driving force behind many of these games is this relatively new understanding: Our brains remain malleable until very late in life.

The concept, called neuroplasticity, means that although we can't make new nerve cells in our brains, we can make new connections between those cells, explained Dr. David Knopman, a neurologist at the Mayo Clinic.

"The idea is that if you can make those new connections, then you could learn to learn better," he said.

The more connections the better, added Terry Barclay, the director of neuropsychology for HealthPartners. "The denser your web of connections, the more it protects against insults and injuries that can happen from aging or from something like Alzheimer's disease," he said.

At her age, Claire Fromme, 26, isn't concerned about dementia. Still, she downloaded a Lumosity app for her iPhone because she frequently misplaces her keys.

One of the games briefly flashes an image of an open suitcase on screen, displaying the suitcase's contents. The object is to recall where the items were placed, then repack the suitcase the way it was originally packed. While the game sounds simple, Fromme said it has helped her.

Recently, when she couldn't find her keys, she tried to picture where she had last seen them. "I could see where they were," she said. "They were on a shelf in my closet where I throw most stuff."

Gary Becker, 68, swears by BrainHQ, which he plays every day on his computer.

After undergoing brain surgery a few years ago, the St. Louis Park man noticed he was having trouble focusing and he often lost his bearings if he turned a corner quickly. In one online game he plays, he must continually try to reorient himself on a digital map. "I can say this has been extremely beneficial," Becker said.

Promising, not proof

In the decadelong brain training study, funded by the National Institutes of Health, researchers tested about 2,800 participants in areas of memory, reasoning and processing speed. Some participants completed several rounds of brain exercises, while others received no exercises.

Roughly 74 percent of the participants who did the exercises retained their ability to do reasoning tasks 10 years later. That compares with 62 percent of those who did not do the exercises. The difference between the groups was even more pronounced when it came to speed of information processing.

In all, 71 percent of those who received speed exercises did as well or better 10 years later, whereas only 48 percent of the participants who did not get the exercises did as well a decade later. Notably, however, the memory training exercises showed no measurable difference a decade later.

Rebok said researchers were surprised by the long-term effects of brain training, adding that the results are promising. But he stopped short of saying the study is an endorsement for brain games on the market.

"Some of these programs are created by well-respected scientists and have a good scientific base supporting them," he said. "A lot of them don't."

Questions remain

Doctors who work with Alzheimer's patients acknowledged the study's merits but also noted its limits.

The findings about the possible benefits of brain training are "very" significant, said Knopman. At the same time, there are many different ways to stimulate the brain, he said.

His advice to patients? "I think it's fine if you want to spend $200 on Lumosity or some other type of brain training," he said. "But I think you can get the same benefits by being part of a Bible study or a book club or discussing current events with your family or reading and doing things that are actually more social than [playing] a computer game, which in some sense is socially isolating."

As for Lehmann, he's simply added his digital brain games to his health regimen, which includes doing yoga, watching his diet and meeting regularly with friends. He's not sure which activities are helping the most.

"It's a strange situation. Without knowing anything definitive of a cure, everything they [recommend] is about keeping active and keeping your mind busy — and I agree with that," he said.

But there's another reason he plays "Memory Matrix" so often on his iPad: "I enjoy it so I keep doing it."

Allie Shah • 612-673-4488