Playing computer games in later life may substantially cut the risk of dementia, according to a new study.

Activities which exercise the brain, including reading novels and playing computer games, can have a protective effect on the mind and help prevent memory loss, it says.

By contrast, watching television for hours on end significantly increased the chance of suffering problems.

The Telegraph reports: ‘The latest research will be seen as further proof that so-called "brain training" machines, such as the Nintendo DS advertised by Nicole Kidman, can help to delay brain decline.’

"This study is exciting because it demonstrates that aging does not need to be a passive process," said Dr Yonas Geda, a neuropsychiatrist at Mayo Clinic in Rochester, Minnesota.

"By simply engaging in cognitive exercise, you can protect against future memory loss."

But she added: "Of course, the challenge with this type of research is that we are relying on past memories of the participants, therefore, we need to confirm these findings with additional research."

More than 700,000 people in Britain suffer from dementia, of which 400,000 have Alzheimer's, the most common form.