Cognitive Screening in Illiterate and Low-Literate Adults: Normative Data Study in Iranian Older Adults

Background The present study sought to establish normative data for five brief, education-fair cognitive screening instruments—the Abbreviated Mental Test Score (AMTS), A Quick Test of Cognitive Speed (AQT), the Picture Memory Impairment Screen (PMIS), the Clock Drawing Test (CDT), and Verbal Fluency (VF)—in a population of Iranian older adults with illiteracy or limited formal education and to investigate age, sex, and education differences in performance on these screening tests. Methods A total of 220 participants aged 58-86 years, with either no formal education or up to six years of schooling, were recruited from municipal health houses across multiple districts of Tehran to ensure representation of diverse socioeconomic strata. Following a comprehensive psychiatric evaluation, eligible individuals completed the AMTS, AQT, PMIS, CDT, and VF assessments, administered by trained psychologists. Participants were stratified into three age groups: 58-64, 65-69, and ≥70 years. Between-group differences were evaluated using analysis of variance (ANOVA) and independent samples t-tests. Linear regression analyses were conducted to assess the impact of each additional year of education on cognitive test performance. Regression-based normative values were derived using models incorporating age (as a continuous variable) and years of education as predictors. Results Inter-rater reliability ranged from moderate to perfect (κ = 0.44-1.00), indicating acceptable to excellent agreement across measures. A total of 220 participants aged 58 to 86 years were included in the analysis. Age and sex did not show significant effect for most instruments; however, significant differences were identified for AQT-CF and PMIS. Educational attainment exerted a significant effect on performance across most measures, with the exception of PMIS. Regression-based normative data were subsequently generated. Conclusion The derived normative data could facilitate the interpretation of cognitive performance in this population through the use of standardized scores ( z -scores and percentiles) in clinical settings.