Six-Item Screener to Identify Cognitive Impairment Among Potential Subjects for Clinical Research :

The clock-drawing test has achieved widespread clinical use in recent years as a cognitive screening instrument and a significant amount of literature relates to its psychometric properties and clinical utility. This review aims to synthesize the available evidence and assess the value of this screening test according to well-defined criteria. A Medline and Psycho-info literature search of all languages was done from 1983 to 1998 including manual cross-referencing of bibliographies. A brief summary of all original scoring systems is provided as well as a review of replication studies. Psychometric data including correlations with other cognitive tests were recorded. Qualitative aspects of the test are also described. Among published studies, the mean sensitivity (85%) and specificity (85%) of the clock-drawing test are impressive. Correlations with the Mini-Mental State Examination and other cognitive tests was high, generally greater than r = 0.5. High levels of inter-rater and test-re-test reliability and positive predictive value are recorded and despite significant variability in the scoring systems, all report similar psychometric properties. The clock test also shows a sensitivity to cognitive change with good predictive validity. The clock-drawing test meets defined criteria for a cognitive screening instrument. It taps into a wide range of cognitive abilities including executive functions, is quick and easy to administer and score with excellent acceptability by subjects. Together with informant reports, the clock-drawing test is complementary to the widely used and validated Mini-Mental State Examination and should provide a significant advance in the early detection of dementia and in monitoring cognitive change. A simple scoring system with emphasis on the qualitative aspects of clock-drawing should maximize its utility. Copyright 2000 John Wiley & Sons, Ltd.

Clinically diagnosed Alzheimer's disease and other dementing illnesses were assessed in a geographically defined US community. Of 3623 persons (80.8% of all community residents over 65 years of age) who had brief memory testing in their homes, a stratified sample of 467 persons underwent neurological, neuropsychological, and laboratory examination. Prevalence rates of Alzheimer's disease were calculated for the community population from the sample undergoing clinical evaluation. Of those over the age of 65 years, an estimated 10.3% (95% confidence limits, 8.1% and 12.5%) had probable Alzheimer's disease. This prevalence rate was strongly associated with age. Of those 65 to 74 years old, 3.0% (95% confidence limits, 0.8 and 5.2) had probable Alzheimer's disease, compared with 18.7% (95% confidence limits, 13.2 and 24.2) of those 75 to 84 years old and 47.2% (95% confidence limits, 37.0 and 63.2) of those over 85 years. Other dementing conditions were uncommon. Of community residents with moderate or severe cognitive impairment, 84.1% had clinically diagnosed Alzheimer's disease as the only probable diagnosis. These data suggest that clinically diagnosed Alzheimer's disease is a common condition and that its public health impact will continue to increase with increasing longevity of the population.

This article reports on a prevalence study of dementia and Alzheimer's disease among two groups of subjects with the same ethnic background but widely differing environments. The study was conducted among residents aged 65 years and older in two communities: Yorubas (N = 2,494) living in Ibadan, Nigeria, and African Americans (N = 2,212 in the community and N = 106 in nursing homes) living in Indianapolis, Indiana. The study design consisted of a screening stage followed by a clinical assessment stage for selected subjects on the basis of their performance on the screening tests. The age-adjusted prevalence rates of dementia (2.29%) and Alzheimer's disease (1.41%) in the Ibadan sample were significantly lower than those in the Indianapolis sample, both in the community-dwelling subjects alone (4.82% and 3.69%, respectively) and in the combined nursing home and community samples (8.24% and 6.24%, respectively). The prevalence rates of dementia and Alzheimer's disease increased consistently with advancing age in both study groups. To the authors' knowledge, this is the first study, using the same research method at the two sites, to report significant differences in rates of dementia and Alzheimer's disease in two different communities with similar ethnic origins.