Cognitive decline is delayed in people who speak two languages on a daily basis, according to new research from Spain.
Dementia is known to be 50% less common in countries where more than one language is spoken. Investigators wanted to see how the degree of bilingualism protects the brain from developing mild cognitive impairment and Alzheimer’s, and by what mechanism.
The study took place in Barcelona, Spain, where the use of Catalan and Spanish is highly variable between neighborhoods, explained lead researcher Marco Calabria, Ph.D.
Participants included 62 who were cognitively healthy, 135 who had mild cognitive impairment, and 68 with Alzheimer’s. The study team used a “bilingualism gradient” when measuring cognitive abilities, ranging from people who speak only one language but are passively exposed to another, to individuals who are highly proficient in both and use them indiscriminately on a daily basis. They found that a certain degree of bilingualism had neuroprotective benefits.
“We saw that the people with a higher degree of bilingualism received a diagnosis of mild cognitive impairment later than those who were passive bilinguals,” said Calabria, of the Open University of Catalonia and Pompeu Fabra University.
This regular switching between languages is related to brain functions such as executive control, which helps people perform several actions at once by filtering out irrelevant information, Calabria said. This system may help offset symptoms of neurodegenerative diseases, he theorized.
“[W]hen something is not functioning well due to the disease, thanks to the fact that it is bilingual, the brain has efficient alternative systems for resolving the problem,” Calabria said. “In fact, active bilingualism is an important predictor of delay in the onset of symptoms of mild cognitive impairment — a preclinical phase of Alzheimer’s disease — because it contributes to cognitive reserve.”
The researchers are preparing to study whether the same phenomenon extends healthy cognition in other brain diseases, such as Parkinson’s and Huntington’s diseases.
Full findings were published in the journal Neuropsychologia.
