Improvement pattern in the clock drawing test in early Alzheimer's disease

The aim of this paper was to compare the performance of a group of patients with early Alzheimer's disease (EAD) against a control group of healthy control (HC) subjects in the Clock Drawing Test (CDT), i.e. verbal command versus copying of a clock model presented to the subject.

The authors have studied 140 subjects; 70 patients with probable EAD, with a mean age of 76.4 +/- 7.64 years and a clinical dementia rating stage 1 (mild dementia), and 70 HC with a mean age of 75.16 +/- 6.34 years.

Patients in the EAD group obtained significantly higher scores on the copy command mode than on the verbal command mode (Z = -7.129, p < 0.001)--improvement pattern of the CDT--whereas no statistically significant differences were found in the HC group (Z = -2.001, p < 0.080). Within the group of EAD patients, we have noticed that there is a correlation between the copy command mode and the visual-constructive functions of the Cambridge Cognitive Examination (CAMCOG) (r = 0.607, p < 0.01), while the memory functions of the CAMCOG correlate with the verbal command mode (r = 0.704, p < 0.01).

In our study, the EAD patients show an improvement pattern in the execution of the CDT copy command in comparison with the execution of the CDT verbal command, which we did not observe in the HC group. Such results might be associated with a greater deterioration of the memory functions when compared with the visual-constructive ones in the patients with EAD.