Elderly people can gain up to an extra 14 years of "cognitive youth" by doing mental exercises, scientists said yesterday.
Volunteers aged 65 and over who did just 10 hours of training sessions to improve their memory, problem-solving and reaction times had mental abilities equivalent to people between seven and 14 years younger than those who did not.
Ian Robertson, a professor of psychology at Trinity College in Dublin, last month published Stay Sharp, a book outlining how mental ageing can be reduced by cognitive exercises and lifestyle changes.
Yesterday, speaking at the BA Festival of Science, Prof Robertson, 54, said that increasing life expectancy and better knowledge of ways of slowing the effects of ageing on the brain were leading to a growing gulf between biological and chronological age. "Our bodies are getting healthier and we are living longer. The main threat to being able to function effectively in old age is the functioning of our brains.
"What neuroscientists have discovered is the human brain is plastic, or shaped by what you learn, at all ages. We all know 80-year-olds who are pretty sharp and people in their fifties or sixties who have lost a lot of cognitive function.
"There is strong evidence that when you get over 50 the degree to which you maintain your function is down to just a handful of factors. Diet, exercise, mental stimulation, mental training and stress are all key factors in determining whether your brain can stay healthy enough for you to enjoy life in the new prime between 50 and 80.
American researchers followed the experiences of almost 3,000 men and women aged between 65 and 94 who volunteered for a mental sharpness training programme.
One group was given memory training, a second trained in problem-solving and reasoning, a third group was shown how to speed up problem-solving and reaction times through computer game-like exercises that became steadily more difficult and a control group received no training.
The training took place in 10 one-hour classes over a six-week period. The volunteers were returned 11 months later for re-assessment.
Those who took the training showed improved cognitive ability when compared with those who did not. Four extra training sessions given a year after the end of the original lessons improved mental abilities even further.
Prof Robertson added it would cost governments less to encourage the elderly to stay mentally fit than to allow them to become dependent on others.