The influence of education on performance of adults on the Clock Drawing Test

ABSTRACT The Clock Drawing Test (CDT) is an important instrument for screening individuals suspected of having cognitive impairment. Objective: To determine the influence of education on the performance of healthy adults on the CDT. Methods: A total of 121 drawings by healthy adults without neurological complaints or impairments were analysed. Participants were stratified by educational level into 4 subgroups: 27 illiterate adults, 34 individuals with 1-4 years of formal education, 30 with 5-11 years, and 30 adults with >11 years' formal education. Scores on the CDT were analyzed based on a scale of 1-10 points according to the criteria of Sunderland et al. (1989).¹ The Kruskal-Wallis test was applied to compare the different education groups. Tukey's multiple comparisons test was used when a significant factor was found. Results: Although scores were higher with greater education, statistically significant differences on the CDT were found only between the illiterate and other educated groups. Conclusion: The CDT proved especially difficult for illiterate individuals, who had lower scores. These results suggest that this screening test is suitable for assessing mainly visuoconstructional praxis and providing an overall impression of cognitive function among individuals, independently of years of education.