Study leader Dr. Tom Schweizer, a neuroscientist at St. Michael's Hospital in Toronto, said this is the first physical evidence that bilingualism delays the onset of the Alzheimer's disease.
Schweizer's team studied computed tomography scans of patients who had been diagnosed with probable Alzheimer's disease -- half of them bilingual, the half unilingual -- and who had similar levels of education and cognitive skills, such as attention, memory, planning and organization.
The study, published in the journal Cortex, found even though both groups performed equivalently on all measures of cognitive performance, the scans of the bilingual patients showed twice as much atrophy in areas of the brain known to be affected by Alzheimer's.
Previous observational studies found bilingualism delayed the onset of Alzheimer's symptoms by as much as five years, but this is the first study to find physical proof via the brain scans, Schweizer said.
Schweizer noted that bilingualism does not prevent Alzheimer's.