Validity of the Clock-Drawing Test as a screening tool for cognitive impairment in the elderly

The authors studied the validity of the Clock-Drawing Test (CDT) in comparison with the Mini-Mental State Examination (MMSE) and the association between the CDT and mortality in a large general population sample of persons aged 75 years or more. Data were obtained from the MRC Trial of the Assessment and Management of Older People in the Community. Baseline assessments were conducted between 1995 and 1999 in the United Kingdom. A total of 13,557 subjects with both CDT and MMSE scores were included in the analysis. The median follow-up period was 4.7 years. The sensitivity and specificity of the CDT for detecting moderate-to-severe cognitive impairment (MMSE score less than or equal to 17) were 77% and 87%, respectively, for nurse administration and 40% and 91%, respectively, for postal administration. Sensitivity was higher among females and increased with age. In Cox proportional hazards regression, a worse CDT score was associated with increased risk of all-cause mortality and mortality from cerebrovascular and respiratory diseases, even after adjustment for potential confounders. The authors conclude that the CDT may have value as a brief face-to-face screening tool for moderate/severe cognitive impairment in an older community population but is relatively poor at detecting milder cognitive impairment.