THE ability to speak more than one language can delay the development of dementia by up to five years, Scottish scientists have discovered.

Research on almost 650 dementia patients found those who were multilingual experienced a slower onset of Alzheimer's disease, vascular dementia and frontotemporal dementia.

The results suggest diverse language skills can significantly stall dementia.

Researchers also found the bilingual advantage extended to illiterate people who had not attended school, confirming that the observed effect was not caused by formal education differences.

The research was done by scientists at the University of Edinburgh in partnership with colleagues at Nizam's Institute of Medical Sciences in Hyderabad, India.

Thomas Bak, of the University of Edinburgh's School of Philosophy, Psychology and Language Sciences, said: "These findings suggest bilingualism might have a stronger influence on dementia that any currently available drugs.

"This makes the study of the relationship between bilingualism and cognition one of our highest priorities."

It has been suggested that alternating between languages may be a form of brain training which could be more effective than any artificial programme.