The effect of illiteracy on performance in screening tools for dementia: A systematic review and meta-analysis

Background The assessment of dementia in individuals who are illiterate is complex. Research indicates that many tools designed for screening dementia are affected by literacy level. However, no systemic analysis exists to evaluate the overall effects of this important confounding factor. We systematically reviewed and meta-analytically estimated the differences in performance in dementia screening tools between literate and illiterate individuals. Method Electronic databases (MEDLINE, PsycINFO, and EMBASE) were searched from 1975 to February 2020 to identify empirical studies examining performance in dementia screening tools in literate and illiterate individuals over 50 years old. Data for effect sizes, participant demographic information, and study information were extracted. Result We identified 28 studies collectively comprising of 28,298 individuals classified as literate and 15,995 individuals classified as illiterate. Of these 28 studies, 19 studies were methodologically suitable for meta-analysis. Multi-level random-effects modelling demonstrated a significant overall effect, with literate participants scoring significantly higher than illiterate participants (g = -1.2962, 95% CI = -1.6200, -0.9723). Moderator analyses indicated significant effects of test type and the presence of cognitive impairment on the extent of the difference in performance between literate and illiterate participants. The difference in performance between groups was smaller in screening tests designed or modified for illiterate individuals (p < 0.05), and in individuals with cognitive impairment (p < 0.01).Conclusion Our findings confirm the unsuitability of many dementia screening tools for individuals who are illiterate. The results of this systematic review and meta-analysis emphasise the need for the development, validation, and use of tools that are suitable for individuals of all literacy abilities.