Secrets of eternal youth identified

Ian Robertson, a neuroscientist from Trinity College, Dublin, said the decline in mental capacity with age can be counteracted by exercise, diet, lifestyle and intellectual outlook. "There is strong evidence that the degree to which you maintain your mental faculty depends on a number of simple environmental and behavioural factors," he said.

He identified the seven factors as: aerobic fitness, a stimulating job, a good education and willingness to keep learning, a minimum of stress, friends and a good social life, a diet rich in oily fish, fruit and vegetables, and the ability to think young.

"If you start to think of yourself as old at the age of 60 then you'll behave old at 60," Dr Robertson said.

"We know that optimists live longer than pessimists, and we know that optimism and mood has effects on the immune system and we know that the immune system is tied in with brain function," he added.