New research suggests that not being able to read or write can raise the chances of developing dementia by two or three times.

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Not being able to read or write may dramatically increase the risk of dementia, according to a new study.

According to the United States Department of Education, 1 in 5 adults in the country do not have the literacy skills required for “comparing and contrasting information, paraphrasing, or making low-level inferences.”

Overall, 43 million U.S. adults have low literacy abilities. Results of a survey that the department conducted between 2011 and 2014 indicate that 26.5 million people in the country do not have the literacy skills mentioned above, 8.4 million have even fewer literacy skills, and 8.2 million could not take part because of a linguistic or cognitive barrier.

Now, new research suggests that people who cannot read or write may have a higher risk of dementia. Jennifer J. Manly, Ph.D., of Columbia University Vagelos College of Physicians and Surgeons, in New York, is the senior author of the paper, which appears in the journal Neurology.

Manly explains the link between literacy and brain health, saying, “Being able to read and write allows people to engage in more activities that use the brain, like reading newspapers and helping children and grandchildren with homework.”

“Previous research has shown such activities may reduce the risk of dementia,” she adds. Indeed, the theory of cognitive reserve suggests that the brain’s flexibility and ability to find alternative solutions to problems may offset the symptoms of Alzheimer’s.

Our new study provides more evidence that reading and writing may be important factors in helping maintain a healthy brain.”

Jennifer Manly, Ph.D.

In the new study, Manly and colleagues surveyed and tested 983 people with low levels of formal education who were living in Manhattan. Most participants had been born and raised in rural parts of the Dominican Republic, where there had been limited access to education.

On average, the study participants were 77 years old, and they had gone to school for a maximum of 4 years.

Based on the participants’ answers to the question, “Did you ever learn to read or write?” the researchers separated them into groups, finding that 237 participants were illiterate and 746 were literate.

At baseline, the participants underwent medical exams and took part in memory and reasoning tests. Then, they retook the tests every 18 months to 2 years for an average of 4 years.

At the start of the study, 83 of the 237 people who could not read or write — 35% of this group — already had dementia. By contrast,134 people from the group of 746 literate participants, or 18%, had this disease.

Adjusting for age, socioeconomic status, and cardiovascular disease revealed that illiterate participants were three times more likely to have dementia at the start of the study.

By the end of the study period, 114 of the 237 people who could not read or write, or 48%, had developed dementia. Meanwhile, 201 of the 746 people who were literate — or 27% — had developed the condition.

After adjusting for socioeconomic status, age, and cardiovascular conditions, the analysis revealed that participants who were illiterate had twice the likelihood of developing dementia while the study was ongoing, compared with those who could read and write.

“Our study also found that literacy was linked to higher scores on memory and thinking tests overall, not just reading and language scores,” Manly says.

These results suggest that reading may help strengthen the brain in many ways that may help prevent or delay the onset of dementia.”

Jennifer Manly, Ph.D.

“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.”

The study’s senior author suggests that future research should examine whether funding more literacy programs would help lower the risk of dementia.

She also acknowledges, however, that the current study did not examine when or how the literate participants had learned to read and write, which may have influenced the results.