The study was conducted through the Rotman Research Institute, part of the Baycrest Research Centre for Aging and the Brain. Bialystok’s research team included psychologist Dr. Fergus Craik, and neurologist Dr. Morris Freedman, an authority on the mechanisms underlying cognitive impairment due to diseases such as Alzheimer's.

Researchers examined the diagnostic records of 184 patients with cognitive complaints. Of that group, 91 were monolingual and 93 were bilingual. The latter included speakers of 25 different languages, the most prevalent being Polish, Yiddish, German, Romanian and Hungarian. They found that 132 patients met criteria for probable Alzheimer's; the remaining 52 were diagnosed with other forms of dementia. Patient data included Mini-Mental State Examination (MMSE) scores (a measure of general cognitive functioning), and years of education and occupation. The MMSE scores were equivalent for the monolingual and bilingual groups at their initial visit to the clinic, indicating comparable levels of impairment.

The researchers determined that the mean age of onset of dementia symptoms in the monolingual group was 71.4 years, while the bilingual group was 75.5 years. This difference remained even after considering the possible effect of cultural differences, immigration, formal education, employment and even gender as influencers in the results.

"There are no pharmacological interventions that are this dramatic," says Dr. Freedman, who is Head of the Division of Neurology, and Director of the Memory Clinic at Baycrest, referring to the four-year delay in onset of symptoms for bilingual patients.

"The data show a huge protective effect," adds co-investigator Dr. Craik, who cautioned that this is still a preliminary finding but nonetheless in line with a number of other recent findings about lifestyle effects on dementia.

The team is working on a follow-up study that will further examine bilingualism and dementia onset. They plan to conduct interviews and cognitive assessments on bilingual and monolingual patients in Baycrest's Memory Clinic and follow them for several years.

The study is published in the February 2007 issue of Neuropsychologia (Vol.45, No.2).

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