Reading between the lines: the association between education, literacy, and dementia in a cohort of older South African adults

Abstract

AbstractBackgroundThe relationship between education and cognitive function in later life has been widely studied, yet it remains uncertain whether the association is due to a true protective effect of education or to test‐taking skills developed through formal education. Literacy, as an objective measure of learning, may clarify this relationship, particularly in low‐ and middle‐income countries (LMIC) where the effect of education may be influenced by school attendance and quality. This study aimed to investigate: 1) the concordance between subjective and objective literacy measures and educational attainment, and 2) the ability of literacy to predict cognitive outcomes.MethodThis study utilized data from Wave 2 of the Health and Aging in Africa: a Longitudinal Study of an INDEPTH Community in South Africa (HAALSI), a population‐based study in Agincourt, South Africa, and its dementia sub‐study (n = 559), collected in 2019‐2020 and 2018‐2019, respectively. Three measures of literacy (self‐report, short sentence reading, reading grade level test) were compared using Cohen’s kappa statistic. Multivariable seemingly unrelated regression (SUR) models were used to examine the association of literacy with cognitive test scores, adjusting for age, sex, and educational attainment. Additionally, multivariable logistic regression models were conducted to assess the independent effect of literacy on dementia risk, controlling for educational attainment.ResultThe Cohen’s kappa score between the three literacy measures was 0.615, indicating substantial agreement. The Cohen’s kappa score between the literacy measures and educational attainment was 0.608. SUR models revealed a statistically significant relationship (p‐value<0.05) between literacy and z‐standardized cognitive test scores in most tests. Literacy was associated with reduced risk of dementia beyond education, with a relative risk ratio of 0.13 (p‐value<0.001) for the literate vs. illiterate groups without education.ConclusionThis study highlights the importance of utilizing objective reading tests to measure literacy in populations, rather than relying solely on self‐reported literacy status. Results indicate that literacy is significantly associated with cognitive function, independent of educational attainment. This suggests that literacy skills acquired outside of formal education may reflect underlying protective factors, such as motivation and resilience, against dementia.