By Olivia Johnson
BBC News, Dublin
Older people should get out there and get the heart pumping if they want to stay sharp of mind, scientists say.
There is plenty to do to keep an agile mind
Studies of the ageing brain have shown mental decline is not inevitable and there are plenty of activities people can do to keep it together "up top".
A healthy diet, aerobic exercise and mental stimulation all helped to keep the mind young, researchers emphasised at a conference in Dublin.
In contrast, prolonged stress and social isolation act to age the brain.
"Neuroscience researchers have made important discoveries that will help keep our brains functioning optimally," Professor Ian Robertson told the British Association's Festival of Science which this year is being held in the Irish capital.
Professor Robertson, dean of research at the Trinity College Institute of Neuroscience, highlighted aerobic exercise as a vital contributor to maintaining brain function as the body ages.
He noted one study in which over-60s who exercised over a three-year period exhibited none of the usual mental decline in that time.
In another study, test subjects obtained mental improvements after just four months of a moderate aerobic training programme.
There are several explanations for the link between fitness of body and mind, according to Professor Robertson.
Exercise increases production of key brain chemicals which encourage the growth of brain and nerve cells and the development of new neural connections.
It also promotes the growth of blood vessels which nourish and sustain existing structures.
"For the over-50s, exercise is a sort of wonder-drug that makes you more mentally agile, less forgetful and delays the loss of sharpness that would otherwise happen," Professor Robertson said.
Continued learning and mental stimulation are also key to retaining ability, according to the scientist, because they "literally grow your brain."
Studies in both humans and animals have shown that brains which are more active develop a richer and more densely connected network of brain cells.
According to Professor Robertson, this brain strengthening may be one factor causing dementia to be less prevalent among people who have spent more time learning.
Advocating a "use it or lose it" approach, the scientist stressed that the decline in mental sharpness usually seen in people over the age of 65 is not inevitable, and can be stopped or even reversed by mental exercise.
In a recent study of nearly 3000 people aged 65 to 94, those given 10 hours of training in memory, problem-solving, and decision-making tasks over the course of several weeks showed marked and lasting increases in cognitive ability.
"Booster" training sessions received a year later resulted in further improvements in mental function which persisted for over a year.
The gained mental ability was equivalent to that which is typically lost by older people over a 7-14 year period.
"The training on average took about a decade off the cognitive age of these volunteers," Professor Robertson explained.