Sydney, Aug 29 - Physical activity, non-smoking, social engagements and mental stimulation cut down the risk of dementia, a new study says.

'What's interesting is that these lifestyle changes ... don't just have benefits for memory and preventing Alzheimer's disease, they can also ward off heart disease and assist in overall well being,' said Leon Flicker, who conducted the study.

Flicker is the director of the Western Australian Centre for Health and Ageing and professor of geriatric medicine at the University of Western Australia (UWA).

'This is big news for people who have memory concerns. These lifestyle changes are not expensive and do not involve pharmaceutical treatment.

'I would encourage everyone who has memory concerns to incorporate these lifestyle changes into their lives - today!'

Dementia has often been thought to be unavoidable and incurable. While the risk of dementia increases with age, dementia is not a natural part of ageing, says an UWA release.

These results have been outlined in the August edition of medical journal Maturitas.