Older people should take a brisk walk three times a week to help reduce the effects of the brain's natural ageing, a new study suggests.
Researchers found that walking briskly for between 30 and 40 minutes three times a week had an effect equivalent to stopping the brain's ageing clock by up to 2 years for a group of 60 to 80-year-olds.
Scientists took brain scans before and after their year-long study, which is among the first to show how exercise can boost brain regeneration and delay the onset of mental decline.
The scans showed that two areas of the brain, which are linked to cognitive decline in later life, grew in volume among those who exercised.
'There is not this inevitable decline that we used to think there was'
But among those who were only given stretching tasks, the prefrontal cortex and hippocampus continued to shrink.
The volunteers were also given a series of tasks to test their memory, attention and language ability. Those who walked three times a week achieved better results than those who didn't.
Professor Kirk Erickson, of the University of Pittsburgh in the US, told the American Association for the Advancement of Science: 'The results suggest that brain and cognitive function of the older adults remain plastic and highly malleable.
'There is not this inevitable decline that we used to think there was. We can improve brain function by relatively modest amounts of physical activity.'