Speaking two languages may
help delay the damage of dementia, a new study suggests.
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 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 Centre 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 Centre 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.
Greater cognitive reserve
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
"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.
"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 Centre 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.
Preserving brain function
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, front temporal dementia, dementia with Lewy bodies
and mixed dementia. Of the total studied, 14% were illiterate.
Those who spoke two
languages developed the symptoms of Alzheimer's disease, front temporal
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
Visit the Alzheimer's Association for more on dementia.