Can clock drawing test help to differentiate between dementia of the Alzheimer's type and vascular dementia? A preliminary study

Objectives: The purpose of this preliminary study was to determine if clock drawing performance may help to differentiate between dementia of the Alzheimer's type (DAT) and vascular dementia (VD) patients. Methods: Eighty-eight community-dwelling outpatients were comprehensively evaluated and met DSM-IV criteria for DAT or VD. Cognitive evaluation included the Mini-Mental State Examination (MMSE) and the Cambridge Cognitive Examination (CAMCOG). CAMCOG derived clock drawings were blindly evaluated by the same investigator, according to Freedman's method for clock drawing, and a total score as well as subscores (contour, numbers, hands and center) were determined. Results: There were no significant differences between DAT and VD patients in terms of demographic (age, gender, education) and cognitive (MMSE score, CAMCOG score) characteristics. On the average, the VD group showed slightly poorer performance on each of the clock drawing test (CDT) measures studied. With application of the Bonferroni correction, only Freedman's total score and hands subscore were statistically different between groups (p < 0.003, p < 0.004, respectively). Stepwise logistic regression analyses showed that the only significant variable was Freedman's total score (B = - 0.273, p = 0.005). Stepwise discriminant analysis identified Freedman's total score as the only significant predictor of diagnosis (Wilkes' lambda = 0.903, p = 0.003). This model correctly classified 65.9% overall into the respective DAT and VD groups. Conclusions: CDT scored according to a comprehensive technique may be of value in differentiating DAT from VD patients. We hypothesize that the classificatory ability of Freedman's method might be attributed to its presumed sensitivity to impaired executive functioning which is more pronounced in VD compared with DAT patients.