A 20-year randomized controlled trial has shown that cognitive speed training, combined with booster sessions, reduces the risk of dementia diagnosis by 25 percent among older adults. The study, involving over 2,800 participants aged 65 and older, focused on a computer-based task requiring quick recall of visual details. While results are promising, experts urge caution due to the study's multiple outcome measures.
The findings come from a landmark study published in Alzheimer's & Dementia: Translational Research and Clinical Interventions, marking the first randomized controlled trial to demonstrate a clear intervention against dementia over two decades.
Conducted on 2,832 individuals aged 65 and older, the trial randomly assigned participants to four groups: speed training, memory training, reasoning training, or a control group with no intervention. The speed training used a task called Double Decision, where participants briefly viewed a scene with a car and a road sign, then recalled the car's identity and the sign's location. The exercise adapted to improve performance, making it progressively challenging.
Training involved two 60- to 75-minute sessions weekly for five weeks. About half of each intervention group received boosters: four one-hour sessions after the first year and four more after the third year.
Twenty years on, analysis of US Medicare claims revealed that only the speed training group with boosters had a significantly lower dementia risk—25 percent less for Alzheimer's or related conditions—compared to controls. Other groups showed no notable reduction.
"The size of the effect is really quite astonishing," said Marilyn Albert of Johns Hopkins University School of Medicine in Baltimore, Maryland. She noted the task's reliance on implicit learning, which produces enduring brain changes without conscious effort. "We know that changes that occur from this kind of learning are very long-lasting," Albert added.
Torkel Klingberg of the Karolinska Institute in Stockholm praised the rigor: "It is impressive to have a 20-year follow-up, and reducing the risk score for dementia is an impressive and important result."
However, Walter Boot of Weill Cornell Medicine in New York cautioned that testing numerous outcomes over 20 years raises the chance of statistically significant results by coincidence. "This does not mean the findings are wrong, but it does mean they should be interpreted cautiously."
Etienne De Villers-Sidani of McGill University in Montreal suggested the training builds brain reserve, delaying cognitive decline, akin to how a single traumatic event like a car crash can create lasting fear.
The study revives interest in brain training amid past controversies, including 2014 open letters from scientists debating its real-world benefits. Andrew Budson of Boston University emphasized broader applications: activities involving implicit learning, such as learning a new sport or craft, may similarly support brain health and delay Alzheimer's effects.
