People who use two languages throughout their life can delay the onset of dementia by four years, research has found.
Previous research has focused on lifestyle factors – such as exercise, education and social life – when looking at how to maintain cognitive ability later in life.
But the study by Canadian scientists, published in Neuropsychologia, suggests bilingualism can help keep the brain sharp.
"We are pretty dazzled by the results," said principal investigator Ellen Bialystok, who led the team from the Rotman Research Institute at the Baycrest Research Centre for Aging and the Brain.
She added: "Our study found that speaking two languages throughout one's life appears to be associated with a delay in the onset of symptoms of dementia by four years compared to those who speak one language."
The study was based on 184 patients with cognitive decline – 91 of whom were monolingual and 93 bilingual.
Alzheimer's is the most common form of dementia which the Alzheimer's Society estimates affects around 120,000 people.