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Does Speaking Several Languages Lower the Risk of Dementia?

A recently published study found that a strong ability in languages may help reduce the risk of dementia. The study of 325 Roman Catholic nuns (75 years or older) in the United States found some differences in the 109 women (33.5%) who developed dementia later in life compared to those who didn't. They found that more years of education was protective. Those speaking 2 or more languages were less likely to develop dementia than women only speaking one language (35% developed dementia) with 4 or more languages the most protective (only 6% of these women developed dementia). However, speaking 2 or more languages did not significantly affect the age at onset of dementia.

But the strongest predictor of later developing dementia was written linguistic ability, especially "idea density". Idea density was viewed as the average number of ideas expressed per 10 written words.180 of the women provided autobiographical essays that they had written decades earlier (in early adulthood) and the researchers looked at the essays for idea density and grammatical complexity. The researchers suggested that written linguistic ability was a measure of "cognitive function" or brain health.

From Science Daily: What multilingual nuns can tell us about dementia 

A strong ability in languages may help reduce the risk of developing dementia, says a new University of Waterloo study.

The research, led by Suzanne Tyas, a public health professor at Waterloo, examined the health outcomes of 325 Roman Catholic nuns who were members of the Sisters of Notre Dame in the United States. The data was drawn from a larger, internationally recognized study examining the Sisters, known as the Nun Study.

The researchers found that six per cent of the nuns who spoke four or more languages developed dementia, compared to 31 per cent of those who only spoke one. However, knowing two or three languages did not significantly reduce the risk in this study, which differs from some previous research.

Tyas added, "Language is a complex ability of the human brain, and switching between different languages takes cognitive flexibility. So it makes sense that the extra mental exercise multilinguals would get from speaking four or more languages might help their brains be in better shape than monolinguals."

The researchers also examined 106 samples of the nuns' written work and compared it to the broader findings. They found that written linguistic ability affected whether the individuals were at greater risk of developing dementia. For example, idea density -- the number of ideas expressed succinctly in written work -- helped reduce the risk even more than multilingualism.

"This study shows that while multilingualism may be important, we should also be looking further into other examples of linguistic ability," said Tyas. "In addition, we need to know more about multilingualism and what aspects are important -- such as the age when a language is first learned, how often each language is spoken, and how similar or different these languages are. This knowledge can guide strategies to promote multilingualism and other linguistic training to reduce the risk of developing dementia."

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