That daily crossword or Sudoku puzzle has just been elevated from fun time waster to vital task.

Australian researchers have found it’s not grey matter that disappears with age, but connecting white matter in the brain.

The research is rewriting the book on how the brain ages, and shows how important it is to undertake mentally engaging tasks into old age.

Researchers found it’s not the brain’s capacity to store memories that fails in latter years, it’s the wiring.

“If you take the analogy of a range of computers, the computers would be the grey matter and the connecting cables would be the white matter,” says Dr Olivier Piguet, a research fellow at Sydney’s Prince of Wales Medical Research Institute.

“The computers still work but the cables stop working, or you lose connections between your network of computers.”

The effect of age-related degenerative conditions, such as Alzheimer’s disease, had encouraged a view that a loss of grey matter was a gradual and unavoidable part of ageing.

But when Dr Piguet and colleagues conducted a post-mortem study of 24 healthy brains they found grey matter was remarkably untouched by time.

The study examined the disease and injury-free brains of Australians, aged 46 to 92.

By taking cross-section images of the brains, and through meticulous measurements, Dr Piquet identified just a five per cent loss in grey matter from the youngest to the oldest brain.

This was eclipsed by a 32 per cent loss of white matter.

Dr Piguet’s study concludes “healthy brain ageing is a process affecting predominantly white matter, not grey matter”.

“This is another piece of the puzzle in trying to understand what is healthy ageing, the normal wear and tear on the brain,” Dr Piguet says.

The research shows how “brain power” – the neurons or nerve cells within grey matter – remains constant throughout life. Instead, what the brain suffers is a loss of connections.

Dr Piguet says the study underscores the need for people to stay mentally and physically active for as long as possible into old age.

Mentally engaging tasks, such as card or board games, or playing musical instruments, are known to prevent the loss of these connections and even foster new ones.

People should not assume that memory loss is an unavoidable part of ageing, Dr Piguet says.

“You can certainly maintain connections, create new connections … there are many studies showing that taking part in new activities will benefit your brain,” he says.

“It’s extremely important to remain active, be out there, play bridge, chess and be physically active as well.”

The study will be published next month in the journal Neurobiology of Aging.

Danny Rose