The role of tests of frontal executive function in the detection of mild dementia

Objective: To compare the performance of patients with mild dementia (Mini Mental State Examination (MMSE) >23), depression (Montgomery-Asberg depression rating scale (MADRS) >12) and controls on tests of frontal executive function (FEF), to see if simple tools could be an adjunct to early recognition of dementia in primary care.

Design: Subjects were required to score above 23 on the MMSE, and to be non-depressed unless in the depression group. Tests of FEF used were a letter based verbal fluency test, a cognitive estimates test, trail marking parts A and B, and a Stroop colour word test. Subjects were followed up at one year to assess long-term outcomes.

Setting: The Thornhill Unit, an old age psychiatry unit, Moorgreen Hospital, Southampton, UK.

Patients: Sixteen patients with a clinical diagnosis of dementia but with normal or borderline MMSE scores, 16 subjects with depression and 19 healthy control subjects.

Results: Subjects with mild dementia scored significantly worse than control subjects on all FEF tests used other than verbal fluency. Subjects with mild dementia were only found to score worse than depressed subjects on the cognitive estimates test and Stroop test, with the Stroop test providing better discrimination between these groups. At follow-up, MMSE scores of both dementia and depression groups were worse.

Conclusions: Many simple tests of FEF can distinguish subjects with mild dementia from controls, although caution must be taken in the presence of depression. Of these tests, the cognitive estimates test may provide a simple test which can be used in conjunction with screening tests for dementia, such as the MMSE. The Stroop colour test was the most successful at distinguishing subjects with mild dementia from those with depression, but was more difficult to use. The depression group remained cognitively impaired at follow-up, despite improvements in depressive symptoms.