A ground-breaking study of 6,000 Australians is assessing whether diet and exercise can dramatically reduce a person's risk of developing dementia — and potentially reverse some of its symptoms.

The Maintain Your Brain study is assessing people across New South Wales aged between 55 and 77 in an attempt to help prevent cognitive decline, and eventually dementia.

Participants are required to improve their nutrition by eating a plant-based Mediterranean diet and keep active with a series of simple exercises, as well as take part in brain training and mental health exercises to improve cognition.