Older people who move around more - even if they are just doing housework - may protect themselves against the effects of dementia, research has shown.
Scientists studied the donated brains of 454 deceased older adults, 191 of whom had been diagnosed with Alzheimer's and other forms of dementia.
Prior to death they had undergone thinking and memory tests over a period of 20 years. Their average age at death was 91.
At an average of two years before death, each participant was given a wrist-worn accelerometer that monitors activity.
Working round the clock, the device recorded everything from walking around the house to fitness routines.
The study found that higher levels of daily movement were associated with better thinking and memory skills.
The pattern remained the same even when the researchers took account of the severity of damage seen in the brains.
"People who moved more had better thinking and memory skills compared to those who didn't move much at all," study leader Dr Aron S Buchman, from the Rush University Medical Centre in Chicago, said.
"We found movement may essentially provide a reserve to help maintain thinking and memory skills when there are signs of dementia present in the brain."
"Exercise might help by strengthening the connections between brain-cells - referred to as cognitive reserve - which makes our brain more resilient to the changes that cause cognitive decline," Dr James Pickett, head of research at the charity Alzheimer's Society, said.
The findings appear in the journal Neurology.
Australian Associated Press