Psychomotor Slowing in Mild Cognitive Impairment, Alzheimer's Disease and Lewy B

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Psychomotor Slowing in Mild Cognitive Impairment, Alzheimer's Disease and Lewy

Body Dementia: Mechanisms and Diagnostic Value.

May 2010

Abstract

Background: Although psychomotor slowing is frequent in Alzheimer's disease (AD)

and Lewy body dementia (LBD), its mechanism and diagnostic value have not been

examined. Objective: To (i) assess psychomotor speed in patients with mild

cognitive impairment (MCI), AD and LBD, (ii) determine the underlying

mechanisms, and (iii) examine whether psychomotor slowing constitutes a useful

diagnostic marker. Methods: Psychomotor speed was assessed in MCI (n = 11) and

mild dementia due to AD (n = 23) or LBD (n = 18) and controls (n = 52) with

visual inspection time (VIT), digital tapping, simple reaction time (SRT) and

choice reaction time (CRT) tests. Results: MCI did not differ from controls.

Both dementia groups showed different patterns. In AD, VIT (p = 0.0001), tapping

(p = 0.021), SRT (p = 0.0001) and decision time (p = 0.0001) were impaired as

compared to controls. In LBD, VIT (p = 0.0001) was very impaired and correlated

with visual hallucinations (p = 0.001); SRT lengthening (p = 0.0001) was related

to attentional disorders (p = 0.0001). Conclusions: Psychomotor slowing of AD is

due to slower perceptuomotor and decision processes. In LBD, psychomotor slowing

is due to visual and attention disorders, and subtle visual disorders contribute

to hallucinations. VIT and CRT are useful diagnostic markers.