Scientists have long known that certain lifestyle routines, levels of intelligence, education, and even exercise could potentially play a role in delaying the onset of certain dementias like Alzheimer’s disease. Now, a researcher from Nizam’s Institute of Medical Sciences in India has released a new study that highlights the protective ability of bilingualism, or speaking two languages, in delaying certain kinds of dementias.

“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,” Suvarna Alladi, author of the study, said in a press release. “Speaking more than one language is thought to lead to better development of the areas of the brain that handle executive functions and attention tasks, which may help protect from the onset of dementia.”

This was the largest study completed on the topic to date, and it was published in an online issue of Neurology. The study reviewed 648 people from India, who had an average age of 66 and a dementia diagnosis. Out of the 648, around 391 spoke two or more languages, and 14 percent could not read. Alladi discovered that people who spoke two languages had delayed onsets of Alzheimer’s disease, frontotemporal dementia, as well as vascular dementia — even if the bilingual person was illiterate. However, the study did not find any extra benefit in multilingualism, or speaking more than two languages.

“These results offer strong evidence for the protective effect of bilingualism against dementia in a population very different from those studied so far in terms of its ethnicity, culture and patterns of language use,” Alladi said in the press release.

Though perhaps the largest study completed so far about bilingualism’s effect on dementia, it is far from the first. In the past, scientists found that speaking two languages may delay dementia by up to four years. This phenomenon has been linked to what is known as the brain’s cognitive reserve or behavioral brain reserve, which has been described as being similar to a car’s reserve tank in providing the brain with “fuel,” which can be expanded by bilingualism or sustained complex mental activity. The authors of a 2003 study wrote that “[t]he concept of cognitive reserve (CR) suggests that innate intelligence or aspects of life experience like educational or occupational attainments may supply reserve, in the form of a set of skills or repertoires that allows some people to cope with progressing Alzheimer’s disease (AD) pathology better than others.” The study went on to state that there is epidemiological evidence that a lifestyle defined by the engagement in intellectual and social activities is linked to slower cognitive decline.

Dr. Ellen Bialystok, a bilingualism researcher at York University in Toronto, told the Wall Street Journal in 2010 that speaking two languages won’t entirely stop the onset of Alzheimer’s or other dementias, but that it could increase this cognitive reserve. “Once the brain runs out of fuel, it can go a little farther,” she said. The benefits of bilingualism lie in the brain function referred to as inhibitory or cognitive control; people who are fluent in two languages must use this skill to stop thinking in one language and focus on another when speaking. But even though research has pointed to its benefits, there’s not enough evidence to prove that picking up a second language, or doing plenty of crossword puzzles, will have that much of an effect on significantly delaying dementia. “[T]here’s no magic point,” Dr. Tamar Gollan, a bilingualism researcher at the University of California San Diego, told the Wall Street Journal.