Longitudinal Changes in Clock Drawing Test (CDT) Performance before and after Cognitive Decline

BACKGROUND Many scoring systems exist for clock drawing task variants. However, none of them are reliable in evaluating longitudinal changes of cognitive function. The purpose of this study is to create a simple yet optimal scoring procedure to evaluate cognitive decline using a clinic-based sample. METHODS Clock-drawings from 121 participants (76 individuals with no dementia and later did not develop dementia after a mean 41.2-month follow-up, 45 individuals with no dementia became demented after a mean 42.3-month follow-up) were analyzed using t-test to determine a new and simplified CDT scoring system. The new scoring method was then compared with other commonly used systems. RESULTS In the converters, there were only 7 items that are significantly different between the initial visits and the second visits. We propose a new scoring system that includes the seven critical items: numbers are equally spaced (12-3-6-9) (p = 0.031), the other eight numbers are marked (p = 0.022), numbers are clockwise (p = 0.002), all numbers are correct (p = 0.030), distance between numbers is constant (p = 0.016), clock has two hands (p = 0.000), arrows are drawn (p = 0.003). Compared with other traditionally used scoring methods, this based change clock drawing test (BCCDT) has one of the most balanced sensitivities/specificities with a clinic-based sample. CONCLUSIONS The new CDT scoring system provides further evidence in support of a simple and reliable clock-drawing scoring system in follow-up studies to evaluate cognitive decline, which can be used in assessing the efficacy of medicine.