Older adults with limited literacy are at increased risk for likely dementia

Low educational attainment, generally measured by years of school completed, is a well-established risk factor for dementia among older adults, with higher education being thought to contribute to cognitive reserve (1). Literacy may be more reflective of educational attainment than years of school completed and thus a more sensitive indicator of risk for the development of dementia. Low literacy is common among elderly adults compared with other age groups (2). In the 2003 National Assessment of Adult Literacy, about one-quarter of older adults were unable to use information presented in text form to accomplish common tasks (2). Further, the association between older age and lower literacy is not merely explained by age differences in years of school completed (3,4). Cross-sectional studies of older adults have shown positive relationships between literacy and global cognition (5–7), memory (6,7), verbal fluency (6,7), and working memory (8) and other executive skills (7), above and beyond the effects of education. Cross-sectional associations between literacy and cognitive performance are not entirely surprising, as reading ability is considered a proxy measure for premorbid intelligence (9). Longitudinal analysis is needed to ascertain whether low literacy might predict cognitive decline or the development of dementia. Two longitudinal studies evaluated the association between literacy and cognitive decline in aging while controlling for education effects (10,11) and found that individuals with lower literacy showed greater decline in memory, language, and executive functioning. Further, literacy has been shown to help explain racial discrepancies in cognitive performance (12) and rates of cognitive decline (13) between black and white elders independent of education. However, few studies have specifically investigated the association between literacy and the development of dementia. Most have been conducted outside of the United States and focused on developing countries by comparing illiterate versus literate individuals (14–16). In a recent study of dementia incidence among older adults in six “middle-income” countries (China, Cuba, the Dominican Republic, Mexico, Peru, and Venezuela) by Prince and coworkers (17), self-reported ability to read a newspaper was associated with lower dementia incidence even after controlling for education and other measures of socioeconomic status. In the present study, we examined the association between literacy and incidence of likely dementia in a biracial cohort of older adults residing in two U.S. cities followed prospectively. We hypothesized that limited literacy, as opposed to adequate literacy, would be associated with greater incidence of likely dementia and that literacy would be predictive above and beyond the effects of education and other participant characteristics.