A new study, published in the 'Alzheimer's & Dementia' journal, has suggested that if healthy older users neglect the proven benefits of physical exercise in favour of the popular games then they could be harming their health.

An international team, which carried out the study, has found "no evidence" that brain exercise programmes "delay or slow progression of cognitive changes in healthy elderly".

In fact, the researchers came to the conclusion after looking at trials undertaken since 1992 on the impact of brain exercises – known as "cognitive training" – on old people.

They found that few trials met their criteria and those that did were often limited or lacking in follow-up.

And, the study concluded that more research is needed into the medium and long-term impact of brain training games which are often advertised in high profile campaigns fronted by Nicole Kidman, Julie Walters and Patrick Stewart.

According to lead researcher Peter Snyder, a global business has developed in brain-training products without any robust proof that they worked.

"Brain ageing products sold today can be a financial drain, decrease participation in more proven effective life-style interventions, like exercise," Prof Snyder of Warren Alpert Medical School of Brown University, Providence, said.

Some products have actually been marketed as weapons in the fight against Alzheimer's disease, but they could also give false hope to the "worried well" about chances of holding back the onset of mental decline, he said.

Neil Hunt, Chief Executive of the Alzheimer's Society, told 'Daily Mail': "One million people will develop dementia in the next 10 years so there is a desperate need to find ways to prevent dementia.

"The idea that 'brain training' may prevent cognitive decline is extremely attractive, but worryingly there is only very limited evidence.