Reading or doing puzzles could be the simplest way of staving off Alzheimer’s disease.

Keeping the brain active and stimulated has been found to have a dramatic effect on reducing the build-up of harmful proteins in the brain.

These destructive fibres, known as beta-amyloid, clump together in plaques, killing off nerves and leading to the symptoms of memory loss and confusion typical of Alzheimer’s.

The condition is incurable but experts believe the key to tackling it – and even stopping it completely – lies in early detection, treating people before the plaques even form.

While previous research has suggested that mentally stimulating activities may help stave off Alzheimer’s, the latest study identifies the biological mechanisms at work and heralds a new way of thinking about how keeping the mind active affects the brain.

Researchers at the University of California, Berkeley, found that brain scans on people with no symptoms of Alzheimer’s who had engaged in stimulating activities all their lives revealed they had fewer deposits of beta-amyloid.

Lead investigator Dr William Jagust said: “These findings point to a new way of thinking about how cognitive engagement throughout life affects the brain.

“Rather than simply providing resistance to Alzheimer’s, brain-stimulating activities may affect a primary pathological process in the disease. This suggests that cognitive therapies could have significant disease-modifying treatment benefits if applied early enough, before symptoms appear.”

Susan Landau, research scientist at the Helen Wills Neuroscience Institute and the Berkeley Lab, who led the research which is published in the journal Archives of Neurology, added: “Amyloid probably starts accumulating many years before symptoms appear.

“The time for intervention may be much sooner, which is why we’re trying to identify whether lifestyle factors might be related to the earliest possible changes.”

Researchers asked 65 healthy, normal adults aged 60 and over to rate how frequently since the age of six they did mentally engaging activities such as reading books or newspapers, and writing letters or email.

Their memories and other brain functions were assessed and their brain scans were compared with those of 10 Alzheimer’s patients and 11 healthy people in their 20s. A significant link was found between higher levels of cognitive activity over a lifetime and lower levels of beta-amyloid.

Dr Simon Ridley, of Alzheimer’s ResearchUK, said: “The authors of this small study suggest there may be benefits to keeping an active mind throughout life. While the study found an association between cognitive activity and levels of amyloid protein in healthy volunteers, we cannot conclude one directly causes the other.”

Dr Anne Corbett, research manager at the Alzheimer’s Society, said: “This is an interesting initial finding. The research involved only a very small number of people and we do not know if they went on to develop dementia. However, we would encourage anyone who enjoys reading, writing and playing games to keep it up.”

Research last year revealed that doing a daily crossword or sudoku puzzle, could halt the advance of dementia as effectively as some drugs.

At least 820,000 people in the UK have a form of dementia with more than half having Alzheimer’s.