Speaking more than one language may result in a slowing of the onset of dementia in old age, a scientific paper suggests.

Researchers at Toronto’s York University reviewed the hospital records of patients who were either monolingual or bilingual  and who all had been diagnosed with dementia. A wide range of languages were spoken by the study participants.

They discovered that bilingual people were diagnosed three to four years after people who spoke one language, according to the paper published Thursday in the journal Trends in Cognitive Sciences.

The average age at diagnosis of dementia was 75.4 years for monolinguals and 78.6 years for bilinguals.

Interestingly, educational level and occupational status favoured the monolingual group, suggesting that those factors were not as critical in the development of dementia as linguistic ability, according to the study.

The researchers describe this process as protecting the "cognitive reserve," meaning that stimulating the brain physically and mentally in effect may protect it from decline.

In the same paper, the researchers also studied how quickly bilinguals and monolinguals complete tasks while distracted. They state that research shows bilinguals may be more adept at switching between tasks and focusing their attention on a given task.

"Lifelong experience in managing attention to two languages reorganizes specific brain networks, creating a more effective basis for executive control and sustaining better cognitive performance throughout the lifespan," says Ellen Bialystok, lead author, in a release.