People who report being illiterate have almost three times the odds of developing dementia when compared with their peers who can read and write, a new study has found.

The researchers followed nearly 1,000 U.S. adults with an average age of 77 years. Many were born and raised in areas of the Dominican Republic where access to formal education was limited. They were given health and cognitive exams over a two-year period.

Among participants who were illiterate, 35% had dementia at the start of the study compared with 18% of those who were literate. Among those who reported being illiterate and did have dementia when the study began, 48% had dementia at an average four-year follow-up. In contrast, 27% of their literate peers had dementia at follow-up.

The study also found that literacy was linked to higher scores on memory and thinking tests overall, not just reading and language scores, said Jennifer J. Manly, Ph.D., from Columbia University, New York. “These results suggest that reading may help strengthen the brain in many ways that may help prevent or delay the onset of dementia,” she said

“Even if they only have a few years of education, people who learn to read and write may have lifelong advantages over people who never learn these skills,” Manly concluded.

The study, “Illiteracy, dementia risk, and cognitive trajectories among older adults with low education,” was published online on Nov. 13 in the journal Neurology.