Speaking Two Languages May Delay Dementia Symptoms
Study of case records found it staved off signs of the disease by more than four years
Wednesday, November 6, 2013
Researchers found that people who were bilingual did not show the signs of three types of dementia, including Alzheimer's disease, for more than four years longer than those who spoke only one language.
The report was published online Nov. 6 in the journal Neurology.
"Bilingualism can be seen as a successful brain training, contributing to cognitive reserve, which can help delay dementia," said study co-author Dr. Thomas Bak, a lecturer at the Center for Cognitive Aging and Cognitive Epidemiology at the University of Edinburgh in Scotland.
Cognitive reserve is the ability of the brain to keep functioning normally despite significant disease or injury, explained Stephen Rao, a neuropsychologist at Cleveland Clinic's Lou Ruvo Center for Brain Health. "It has been understood that this capacity is influenced by education, higher occupational status, engagement in higher order cognitive [thinking] activities, and now bilingualism," Rao said.
People with a greater cognitive reserve experience the onset of dementia later in life than people with less reserve. As a result, the impact of dementia will be less apparent for longer in people with greater reserve capacity, as thinking and memory functions are able to carry on even with the loss of brain cells.
Bak noted that the effect that speaking two languages had in delaying dementia had nothing to do with the level of education of the participants, but may well be another aspect of cognitive reserve.
"The fact that bilingual advantage is not caused by any differences in education is confirmed by the fact that it was also found in illiterates, who have never attended any school," he said.
Another expert agreed.
"This looks to me like a specific effect of language training and plasticity over and above the well-known effect of education," said Dr. Sam Gandy, director of the Mount Sinai Center for Cognitive Health in New York City.
This is reminiscent of the benefit of social engagement that is over and above that of education and mental stimulation, Gandy pointed out.
"This illustrates that there may yet be many ways to help stave off dementia, once we have sufficient ways to stimulate the brain," Gandy said.
There have been other studies that have shown that people who are bilingual have a delayed onset of Alzheimer's disease, Rao said.
"This is another thing we can add to the list of mental abilities that seem to preserve brain function despite the fact that the brain may be ravaged by a disease like Alzheimer's disease and other forms of dementia," Rao added.
For the study, Bak's team evaluated the case records of 648 people from India who had been diagnosed with dementia. Of these patients, 391 spoke two or more languages.
Of those studied, there were 240 people with Alzheimer's disease, the rest had other types of dementia including vascular dementia, frontotemporal dementia, dementia with Lewy bodies and mixed dementia. Of the total studied, 14 percent were illiterate.
Those who spoke two languages developed the symptoms of Alzheimer's disease, frontotemporal dementia and vascular dementia later than people who spoke only one language, the investigators found. This later development of dementia was also found in people who could not read.
There was no added benefit in speaking more than two languages, the researchers pointed out.
The benefit of being bilingual was independent of other factors, such as education, sex, occupation or whether patients came from urban or rural areas, the study authors noted.
While the study found an association between speaking two languages and mental ability, it didn't not prove cause-and-effect.
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