Does the clock drawing test predict cognitive decline in older persons independent of the mini-mental state examination?

OBJECTIVE: To evaluate the value of the Clock Drawing Test (CDT) in predicting cognitive deterioration over a 4-year period, independent of baseline cognitive status evaluated by the Mini-Mental State Examination (MMSE). DESIGN: A preplanned analysis of data collected during the second (1991) and the third (1995) follow-up of the Italian rural cohorts of the FINE Study (Finland, Italy, the Netherlands Elderly). SUBJECTS: Of the 427 men (mean age 77.6 +/- 4.1 years; range 72-90 years) interviewed in 1991, 264 survived and were reinterviewed in 1995. The study population included 247 persons who were interviewed and received a complete cognitive evaluation in both 1991 and in 1995. MEASUREMENTS: Cognitive assessment in 1991 included the MMSE, the Dementia Rating Scale (DRS), and the CDT. The CDT was classified as normal or pathological, based on previously established criteria. The MMSE and the DRS were repeated in 1995. RESULTS: Independent of age and baseline MMSE score, subjects with pathological CDT compared with normal CDT had lower MMSE scores at follow-up (P < .01). These results were also confirmed by evaluating cognitive decline through its impact on change over time in daily life autonomy, as measured by the DRS (P < .01). Among persons scoring more than 21 on the MMSE, compared with persons with a normal CDT, those with pathological CDT performance were 5.4 (95% CI: 2.1-14.2) and 5.5 (95% CI: 1.6-19.6) times more likely to have a MMSE score below 21 and 18, respectively, 4 years later, independent of age and baseline MMSE score. CONCLUSIONS: Findings suggest that the CDT identifies older persons at high risk of cognitive decline and adds prognostic information that supplements the standard MMSE test.