Study details

The new study was a long-term follow-up of the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) trial. The ACTIVE trial began in 1998 and is a large, randomized controlled trial funded by NIH that enrolled almost 3,000 participants ages 65 and older. Participants were from six different geographical areas and didn't have any significant cognitive impairment prior to the study.

Around 25% of patients in the ACTIVE study were minorities, and a majority were women. Women are especially vulnerable to Alzheimer's disease, developing dementia at almost twice the rate of men.

Participants in the study were separated into one of three cognitive training programs: speed training, memory training, or reasoning training. There was an additional control group that didn't receive any form of cognitive training.

According to Sanjula Singh, a physician-scientist and instructor in neurology at Harvard Medical School, speed training was designed to teach the brain to process information more quickly and accurately. In the speed training in the study, participants were asked to identify objects on a screen quickly and make a decision about them.

Marilyn Albert, a coauthor on the study and director of the Johns Hopkins Alzheimer's Disease Research Center, said that what happens during speed training is a similar thought process to what happens when we drive.

"If we're driving in a car and we have all these things going on in the periphery that we're paying attention to, we have to decide what's important and what's not," she said.

Meanwhile, in memory training, participants were taught strategies for remembering lists of words and details of stories, and in reasoning training, participants worked on the ability to solve problems that follow a serial pattern, like identifying the pattern within a series of letters or numbers.

Study participants were initially assigned to do up to 10 sessions of training, twice a week, for 60 to 75 minutes per session over five weeks. Roughly half of the participants in each training group also got additional booster training for up to 23 hours over a three-year period.

The researchers then tracked medical records through Medicare over a 20-year follow-up period to determine which patients were diagnosed with dementia. Various forms of dementia, including Alzheimer's, vascular dementia, and frontotemporal dementia were all grouped into one category.

Overall, the study found that the participants in the speed training group who also received the booster sessions had a 25% reduced risk of developing Alzheimer's and other types of dementia over the 20-year follow-up period compared to the control group.

Those in the memory and reasoning training groups, as well as those in the speed training group who did not receive any booster sessions, did not see any protection against dementia.

"Once the brain rewires for these skills, the change is durable even without continued practice," said Singh. "A child can learn how to ride a bike in about 10 hours, and afterwards that learning lasts a lifetime."

According to Albert, speed training is thought to be similar and could create long-lasting changes in the brain. The brain's ability to adapt and rewire itself in response to the things we learn throughout our lives is often referred to as neuroplasticity.

Kellyann Niotis, a preventive neurologist and clinical assistant professor of neurology at Weill Cornell Medicine, said that speed training could also have greater effects on what's called cognitive reserve, which is the ability of a healthy brain to resist the effects of developing dementia. Cognitive reserve is built over time through factors like education, mentally stimulating activities, and social engagement.

"I think it's that this visual processing speed-based training may be engaging broader neuronal networks that are actually building more brain resilience or more cognitive reserve," she said.

Albert also noted that speed training may be more beneficial because it's adaptive, meaning the difficulty changed based on how well someone performed. This means people who were faster at the beginning moved to even faster challenges quickly, something that didn't occur in the other forms of training.

Thomas Wisniewski, director of cognitive neurology at NYU Langone Health, said the results of the study were "astonishing" and added that the study is the strongest evidence to date that he's seen supporting the use of cognitive training.

"It's really the first clear documentation in a randomized controlled trial that at least some form of cognitive training can lower the risk of dementia," he said.

Based on the results of the study, Albert said that for now, she'd recommend her patients who are over 65 years old to do speed training. However, she noted that since research has suggested brain changes associated with Alzheimer's can start decades before the disease actually develops, it's possible that people who start at a younger age, like in their 40s or 50s, could also see a protective effect.

Experts emphasized that while the results of the study are impressive, Alzheimer's disease and other forms of dementia are complicated and without a singular fix.

"Anyone with a brain is at risk of Alzheimer's and everyone out there should be paying attention to their brain health," said Richard Isaacson, a preventive neurologist at the Institute for Neurodegenerative Diseases.