People who speak two languages develop Alzheimer’s and other forms of dementia nearly five years later than their peers who speak only one language. It is the largest study to date to show that acquiring a language, an intellectually challenging task, can help to keep the brain robust into old age.

For the study, published in the journal Neurology, researchers studied 648 men and women in India who had been diagnosed with Alzheimer’s or other forms of dementia. Sixty percent of them were fluent in two or more languages. Some could not read, though India is a society where people often learn to speak more than one language, regardless of whether they are formally schooled.

On average, those who spoke more than one language were notably older when they were diagnosed with dementia than those who spoke only one. Those who were bilingual developed memory loss and other symptoms at an average age of 65.6 years, compared to 61.1 years for their monolingual peers.

Being bilingual provided advantages even in those who were illiterate and had little formal education. Having few years of schooling has been recognized as a risk factor for Alzheimer’s.

“Our study is the first to report an advantage of speaking two languages in people who are unable to read, suggesting that a person’s level of education is not a sufficient explanation for this difference,” said study author Suvarna Alladi, DM, with Nizam’s Institute of Medical Sciences in Hyderabad, India.

The researchers suggest that being bilingual provides regular brain stimulation since it requires that someone switch regularly between different sounds, words, concepts and grammatical structures. That’s one reason that some advocate that to keep mental skills sharp, we regularly engage in crossword puzzles, word games and other intellectually stimulating activities

The results provide further evidence for the so-called cognitive reserve hypothesis of brain function. According to this theory, intellectually challenging activities build a robust network of connections between brain cells. If, later in life, a disease like Alzheimer’s destroys brain cells, enough connections remain to keep memory and thinking skills sharp, at least for a time.

“These findings suggest that bilingualism might have a stronger influence on dementia than any currently available drugs,” said Thomas Bak of the University of Edinburgh’s School of Philosophy, Psychology and Language Sciences, another study author. Until more effective treatments for Alzheimer’s become available, intellectual stimulation – whether it involves completing a regular crossword puzzle, taking a language course, learning to play a musical instrument or reading a novel — may be a wise investment in your brain health.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by William J. Netzer, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: S. Alladi, TH Bak, V Duggirala, et al: “Bilingualism Delays Age at Onset of Dementia, Independent of Education and Immigration Status.” Neurology, Nov. 6, 2013.