Longitudinal assessment of cognitive function by clock drawing in older adults

To test the hypotheses that performance on a clock-drawing task (CDT) diminishes over time and that poor performance is associated with development of dementia and reduced survival.

Participants in the population-based Leisure World Cohort Study were asked to complete a CDT in follow-up questionnaires mailed in 1992 and 1998. Dementia status was determined using in-person evaluations, follow-up questionnaires, hospital data, and death certificates.

Of the 4,842 cohort members (mean age 80 years) who completed the CDT in 1992, 1,521 also completed it in 1998. Although performance in the CDT diminished over time in only a proportion of the cohort, the mean total score and the percentage of subjects with correctly drawn clocks decreased with each successive 5-year age group (p = 0.0001) and over time. Mean scores were lower in non-demented subjects later identified as demented compared with those who remained free of dementia. A low CDT score in 1992 was associated with a 28% increased risk of dementia and 13% reduced survival.

A CDT may help predict cognitive decline and future disability in the elderly. Identification of high-risk individuals using a CDT may lead to earlier diagnosis and treatment and improved patient management.