A new study has shown that people who speak more than 1 language, tend to develop dementia up to 5 years later than those who are monolingual.

A team of scientists examined almost 650 dementia patients and assessed when each one had been diagnosed with the condition. The study was carried out by researchers from the University of Edinburgh and Nizam's Institute of Medical Sciences in Hyderabad (India).

They found that people who spoke two or more languages experienced a later onset of Alzheimer's disease, vascular dementia and frontotemporal dementia.

The bilingual advantage extended to illiterate people who had not attended school. This confirms that the observed effect is not caused by differences in formal education.

It is the largest study so far to gauge the impact of bilingualism on the onset of dementia - independent of a person's education, gender, occupation and whether they live in a city or in the country, all of which have been examined as potential factors influencing the onset of dementia.

The team of researchers said that further studies are needed to determine the mechanism, which causes the delay in the onset of dementia.

The researchers suggest that bilingual switching between different sounds, words, concepts, grammatical structures and social norms constitutes a form of natural brain training, likely to be more effective than any artificial brain training programme.