Background: Literacy is correlated with general intelligence and is often used to estimate premorbid intelligence in persons with dementia. However, little is known about the relationship between literacy and specific cognitive domains.
Methods: Study participants were 664 community-living adults aged 65 years or older who were participating in a community-based study of health and function in Sonoma, California. Literacy was measured using the North American Adult Reading Test, which evaluates the ability to pronounce words with irregular spellings (such as indict). Cognitive function was assessed using a neuropsychological test battery that included the Mini-Mental State Examination and measures of attention and executive function (Trails B, Stroop, Digit Symbol), verbal learning and memory (California Verbal Learning Test), and verbal fluency (letter "s," animals).
Results: The mean age of the participants was 76 years, 50% were women, 97% were white, and 92% had 12 or more years of education. A strong, linear association was observed between literacy and all cognitive measures (all p <.001). Results were similar after adjustment for age, sex, education, and health-related covariates and were consistent in subgroups of the study population (e.g., women vs men; English vs other native languages). Education was not associated with most cognitive measures after adjustment for literacy.
Conclusions: Literacy is strongly associated with cognitive function across all cognitive domains in well-educated, elderly white persons. Future studies should determine whether interventions to improve lifetime literacy may help prevent cognitive deterioration with age.