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.

摘要 画钟测验（Clock Drawing Test, CDT）是筛查疑似认知障碍人群的重要工具。
研究目的：明确受教育程度对健康成年人完成画钟测验表现的影响。
方法：本研究共分析了121份来自无神经系统主诉或功能损伤的健康成年人的画钟作品。按受教育程度将受试者分为4个亚组：27名文盲成年人、34名接受过1~4年正规教育者、30名接受过5~11年正规教育者，以及30名接受过11年以上正规教育者。参照Sunderland等人（1989）的评分标准¹，采用1~10分制对画钟测验得分进行分析。采用克鲁斯卡尔-沃利斯（Kruskal-Wallis）检验比较不同受教育程度组间的差异，若发现存在统计学显著性差异，则采用图基（Tukey）多重比较检验进行后续分析。
结果：尽管受教育程度越高，画钟测验得分越高，但仅在文盲组与其他各受教育组之间发现了具有统计学意义的得分差异。
结论：画钟测验对文盲群体而言难度尤高，其得分更低。本研究结果表明，该筛查工具主要适用于评估视空间建构运用能力，并可整体反映个体的认知功能状态，不受受教育年限的影响。