Controversial study claims this simple brain exercise can cut dementia risk by 25%

Further research is still needed to prove effects of such exercise, scientists say

Scientists have identified a type of mental exercise focused on processing speed that could cut people’s risk of developing dementia in later life by 25 per cent, an advance that may lead to new interventions for the elderly.

Brain training as an approach to prevent dementia has been a hotly debated topic. While earlier studies suggested it could lead to interventions against the condition, many cognitive scientists pointed out that these previous research could be overstating their claims.

In 2014, over 70 scientists published an open letter arguing there’s no conclusive evidence that brain training produced dementia-protecting benefits. But just months later, another open letter by 100 scientists countered these claims.

Several brain-training games and apps that were developed over the years also claimed to fight off dementia-related cognitive decline, but there have been very few long-term clinical studies proving their effectiveness.

Now, the latest results from a decades-long randomised controlled trial enrolling hundreds of participants suggest cognitive training involving speed can cut dementia risk or delay its onset in older adults.

“No prior cognitive training intervention has been shown to reduce the risk of ADRD (Alzheimer's Disease and Related Dementias) over a 20-year period,” researchers wrote in the study published in the journal Alzheimer's and Dementia: Translational Research & Clinical Research.

However, researchers not involved in the study urge caution in interpreting the results.

Elderly people at Saint-Vincent retreat house (AFP via Getty Images)

The clinical trial began enrolling participants in the late 1990s and included over 2,800 people aged 65 or older.

Participants were randomly assigned to practice one of three different types of brain training, testing their processing speed, memory, or reasoning, or to a control group.

These trainings involved computerised tests where participants had to find visual information quickly, handling increasingly complex stimuli in shorter time windows. The tests were also adaptive, with the challenge increasing as a participant improved, with faster presentations and more complex visual arrays.

Participants also had to respond rapidly while managing their attention across several aspects of the task.

They first did an hour-long training session twice a week for five weeks, and one to three years later, they did four booster sessions. In a follow-up after five, 10 and 20 years, the study found speed training was "disproportionately beneficial".

In comparison, scientists found that memory or reasoning training did not show statistical significance in reducing dementia risk in later life.

“Memory and reasoning training utilised ‘declarative memory’...whereas the speed training involved ‘procedural memory’,” researchers explained.

“Importantly, individuals in the speed group who did not complete the initial speed training, or any of the booster sessions, did not show a significantly lower risk of diagnosed ADRD over the follow-up period,” scientists wrote in the study.

“Cognitive training involving speed of cognitive processing has the potential to delay the diagnosis of Alzheimer's disease and related dementias (ADRD),” researchers concluded.

Alzheimer’s researchers, not involved in the research, welcome the long-term analysis but caution that some claims made in the study are questionable.

“With around 20 years of follow-up, it provides a valuable and encouraging contribution to an area where long-term evidence is rare,” said Susan Kohlhaas, executive director at Alzheimer’s Research UK.

Citing a limitation of the study, Dr Kohlhaas said “diagnoses were identified through health records rather than specialist clinical testing”.

“So we do not know whether this training changed the underlying diseases that cause dementia or affected specific types of dementia,” she explained.

“Further research is now needed to understand how this type of training might work, who could benefit most, and how it fits alongside the strongest evidence we already have for protecting brain health, including staying physically active, managing heart health and keeping socially connected,” Dr Kohlhaas said.

Moreover, the study excluded people with conditions such as poor vision or hearing, meaning its findings are not fully representative.

“Further research is still needed to determine whether cognitive training can reduce the risk of dementia,” said Baptiste Leurent, professor of medical statistics at University College London.