The Times They Are a-Changin': Clock Drawing and Prediction of Dementia

Identification of individuals who will eventually develop dementia is critical for early intervention, treatment, and care planning. The clock drawing test (CDT) is a widely used cognitive screening tool that has been well accepted among clinicians and patients for its ease of use and short administration time. This review explores the value of the CDT for predicting the later development of dementia in cognitively intact older adults and patients with mild cognitive impairment (MCI). Additionally, we reviewed studies that examined the ability of the CDT to monitor declines in cognitive functioning over time. A PubMed literature search for articles that included a longitudinal analysis of the CDT was conducted. The search included articles published up to June 2013 and manual cross-referencing of bibliographies. Relevant studies were categorized, summarized, and critiqued. The consensus from the studies reviewed suggests that the CDT is a useful measure of cognitive decline over time. Conceptual clock drawing errors (eg, misrepresentation of time) detected this decline most effectively. In addition, the CDT appears to differentiate at baseline between cognitively intact older adults who will develop dementia up to 2 years postbaseline. Finally, the CDT has been found to differentiate between patients with MCI who will progress to dementia up to 6 years postbaseline. The CDT appears useful for the longitudinal assessment of cognitive impairment and together with other validated measures may be helpful for predicting conversion to dementia. Cost-effective and practical ways of predicting risk of dementia will become increasingly critical as we develop disease-modifying treatments.