Does the Clock Drawing Test predict dementia? Results of the Leipzig Longitudinal Study of the Aged (LEILA 75+)

Abstract

Background/Objectives: Being diagnosed with dementia has an enormous impact on the patients themselves as well as on caregivers and the society. Therefore research aims to identify individuals at risk prior to a diagnosis of dementia in order to maximise preventive and treatment efficacy. In recent years, research on the preclinical detection of dementia focused on the concept of mild cognitive impairment (MCI), a transitional phase between normal aging and dementia. Patients diagnosed with MCI are more likely to develop dementia compared to normal control groups and therefore represent a high-risk group. However, establishing a diagnosis of MCI often is time consuming. The Clock Drawing-Test (CDT) has been widely used to screen for dementia, especially because of its easy, quick and simple administration and good acceptance among elderly patients. Nonetheless, it is still questionable whether the CDT is an appropriate instrument to identify persons at an early stage or at a high risk of onset of dementia. Methods: Data were derived from the Leipzig Longitudinal Study of the Aged (LEILA 75+), a population-based study of individuals aged 75 and over. In this study the CDT version of Shulman et al. was used. MCI was diagnosed according to the international consensus criteria of Winblad. The cognitive criteria for a dementia diagnosis were based on the „Structured Interview for the Diagnosis of Dementia of Alzheimer type, Multi-infarct Dementia and Dementia of other Etiology according to DSM-III-R, DSM-IV and ICD-10“ (SIDAM) or, with proxy interviews, on the „Clinical Dementia Rating Scale“ (CDR). The CDT scores and diagnosis of MCI between patients developing and patients not developing dementia were compared. Multivariate analyses (Cox proportional hazard models, Kaplan-Meier), receiver operating characteristic analyses, and sensitivity and specificity of the CDT were calculated. Results: A total of 7.3% subjects of the initial population were diagnosed with dementia at the following assessment, on average 1.4 years after the initial assessment. Individuals developing dementia at follow-up more often had an initial diagnosis of MCI (64.3% vs. 9.3%) and showed significantly higher CDT scores (2.64 vs. 1.82) compared to those not developing dementia during the study course. The results of the multivariate analysis also revealed that CDT and MCI had a significant effect on a future diagnosis of dementia after adjusting for different confounding variables. The area under the curve was 0.700 (p<0.001) for predicting dementia by using the CDT, and 0.775 (p<0.001) by using MCI-diagnosis. According to the best ratio of values of sensitivity and specificity, the best cut off point was at a CDT score of 3 points. However, the values of sensitivity (67.9%) and specificity (65.2%) were not adequate for predicting a diagnosis of dementia. Discussion/Conclusions: The Clock Drawing Test significantly differentiated between patients developing dementia and patients not developing dementia during the course of the study. Although our results indicate that a diagnosis of MCI is slightly better in predicting dementia than the CDT, the quality of prediction is insufficient for both. While diagnosing MCI is very time consuming, the CDT's major qualities are its quick application and scoring. Further research should therefore aim at improving the CDT scoring system which should focus in more detail on the placement and the size of the hands in order to increase predictive validity. Funding: German Federal Ministry of Education and Research (grant no. 01 ET 0728), and Interdisciplinary Research Cluster of Genetic Factors, Clinical Phenotypes and Environment (LIFE Centre, University of Leipzig). Keywords: Outcome assessment, Clock Drawing Test, dementia.