Illiteracy Tied to a Threefold Increased Risk of Dementia

Damian McNamara

November 26, 2019

Individuals who cannot read or write have significantly increase risk of dementia compared with their literate peers, new research shows.

The latest results from the ongoing Washington Heights-Inwood Columbia Aging Project (WHICAP) showed adults age 65 and older who were unable to read or write had a threefold increase of dementia at baseline compared with their literate counterparts

In addition, individuals who were illiterate but had no dementia at baseline were twice as likely to develop incident dementia.

"Illiterate patients may be at increased risk of developing dementia, and should be monitored accordingly," senior author Jennifer J. Manly, PhD, Columbia University Vagelos College of Physicians and Surgeons, New York, told Medscape Medical News.

People self-reported illiteracy by answering yes or no to the question: "Did you ever learn to read or write?" One of the key take-home messages from the study is that "is that early life educational opportunities have an influence on dementia risk in later life," she added.

The study was published online November 13 in Neurology.

US Illiteracy Rate High

An estimated 32 million people in the United States are illiterate. Given this, said Manly, the findings may have important public health policy implications for an estimated 10% of the population.

Investigators assessed 983 adults who reported four or fewer years of education who were participants in WHICAP, a community-based, prospective cohort study of dementia in the ethnically diverse neighborhoods of Northern Manhattan, New York. Participants were enrolled in the study at one of three time points — 1992, 1999, or 2009.

An objective reading test administered to a subset of the study population helped validate self-reported literacy status.

Participants also underwent a battery of cognitive, functional, and health measures at baseline and follow-up assessments. Next, the investigators compared rates of baseline dementia, risk for incident dementia, and the rate of cognitive decline between the 237 illiterate participants and 746 literate participants.

A clinical consensus conference of neurologists, psychiatrists, and neuropsychologists diagnosed 95% of affected participants with Alzheimer's disease (AD) dementia. The remainder had Lewy body or vascular dementia.

The researchers examined prevalent and incident dementia and found an increased likelihood of prevalent dementia in the illiterate group compared with literate participants in an unadjusted model (odds ratio [OR], 2.35; 95% confidence interval [CI], 1.70 - 3.26).

Illiterate participants also remained at increased odds for prevalent dementia in an analysis that adjusted for potential confounders (OR, 2.65; 95% CI, 1.55 - 4.50).

The risk of developing incident dementia also was elevated among illiterate participants compared with literate participants in an unadjusted Cox model (OR, 1.95; 95% CI, 1.46 - 2.60). Adjusting for covariates reduced the risk of dementia (OR, 1.63; 95% CI, 1.12 - 2.36).

Closer to the Dementia Threshold

Although several prior studies suggest the effect of education on dementia risk is greater for women vs men, the current research did not show any effect of literacy based on sex or gender.

Interestingly, although Illiterate adults demonstrated worse cognition at baseline, they did not experience a more rapid rate of cognitive decline compared with literate participants.

This finding could mean "illiterate adults are closer to the cognitive and functional thresholds for dementia than literate individuals," the researchers note.

"This study adds to this literature by associating illiteracy with increased risk of incident dementia and poorer cognitive abilities. The effect of literacy on dementia risk remained robust even after including potential early and later life confounds of literacy (i.e., socioeconomic status, poorer overall health)," they add.

"One of our next goals is to elucidate the neuroanatomical substrates associated with this increased risk of dementia among older adults with low literacy," Manly said.

The researchers are currently evaluating brain MRI scans on a subset of study participants.

"We will be able to evaluate if there are neuroanatomical structural differences among illiterate and literate participants, and whether this is associated with higher dementia risk," Manly added.

Another future aim is to determine if literacy programs can improve cognitive aging and reduce dementia risk. "We'd love to partner with adult literacy programs to determine if learning to read and write as an adult provides cognitive benefits in older age," Manly said.

Not Surprising

Commenting on the study for Medscape Medical News, Anil K. Nair, MD, director of the Alzheimer's Disease Center in Quincy, Massachusetts, said the threefold increased dementia risk in individuals who were unable to read and write was not surprising.

"The diagnosis of dementia was by memory test, which is very dependent on language, so it was also a proxy for language," said Nair, who is also a fellow of the American Academy of Neurology.

Nair added that he would like to see the same study done at the protein levels, noting that it would be interesting to see whether literacy/illiteracy correlates with tau or amyloid protein levels.

The study was funded by a grant from the NIH National Institute of Aging. Manly and Nair have disclosed no relevant financial relationships.

Neurol. Published online November 13, 2019. Abstract

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