All of the adults currently spoke or had spoken anywhere from two to seven languages, but 44 of the 230 study participants (19 percent) had impaired mental function.
Seniors who were fluent in three languages were nearly four times as likely as their bilingual peers to be protected against cognitive impairment, the researchers found. Those who spoke four or more languages were more than five times as likely as bilingual seniors to be protected against memory problems, according to the study authors.
The association remained true even after the researchers took into consideration age and years of education.
"We showed multilingualism protects from cognitive impairment and, because the earliest stage of Alzheimer's disease is the occurrence of cognitive impairment, it's probably not too audacious to think that multilingualism could delay or lower the risk of [Alzheimer's disease] onset," said Perquin.
The researchers were unable to tease out a difference between seniors with current, rather than prior, fluency in multiple languages, and were unable to say exactly why multilingualism is so important in reducing the risk of cognitive impairment.
"We still have so many things to learn about brain capacities," Perquin said.
One potential explanation, according to Dr. Richard Lipton, a neurologist at Albert Einstein College of Medicine in New York City, is the "'use it or lose it' theory of brain function," he said. "You have to use more of your brain to speak multiple languages."
"There's been a longstanding notion that engagement in cognitively stimulating activities protects against Alzheimer's disease," he added. "Speaking multiple languages is a form of cognitive stimulation."
Lipton said he views Perquin's findings in the context of his "crossword puzzle study." Formally known as the Einstein Aging Study, it found that engaging in mentally stimulating activities, like doing crossword puzzles, may prot
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