Bilingualism Has Protective Effect In Delaying Onset Of Dementia

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Canadian scientists have found astonishing evidence that the lifelong use of two languages can help delay the onset of dementia symptoms by four years compared to people who are monolingual. Now scientists with the Rotman Research Institute at the Baycrest Research Centre for Aging and the Brain have found the first evidence that another lifestyle factor, bilingualism, may help delay dementia symptoms. The study is published in the February 2007 issue of Neuropsychologia (Vol.45, No.2).

In this present study, researchers set out to answer that question by examining the diagnostic records of 184 patients who came to Baycrest's Sam and Ida Ross Memory Clinic between 2002 and 2005 with cognitive complaints. Of that group, 91 were monolingual and 93 were bilingual. The bilinguals included speakers of 25 different languages, the most prevalent being Polish, Yiddish, German, Romanian and Hungarian.

Researchers found that 132 patients met criteria for probable Alzheimer's; the remaining 52 were diagnosed with other dementias. Patient data included Mini-Mental State Examination (MMSE) scores (a measure of general cognitive functioning), 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 age of onset of cognitive impairment was determined by the interviewing neurologist at the first clinic visit who asked patients and their families or caregivers when symptoms were first noticed.

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 a few years.