NEUROPSYCHOLOGICAL PREDICTION OF DEMENTIA IN PARKINSONS-DISEASE

Objective-To identify neuropsychological characteristics predictive of later dementia in Parkinson's disease. Methods-A comprehensive neurop sychological test battery was administered to a cohort of 89 initially non-demented patients with Parkinsons disease consecutively enrolled at a specialised Parkinson's disease clinic. They were reassessed afte r a mean of 3.5 years for the diagnosis of dementia. The Cox proportio nal hazards model was used to identify baseline characteristics predic tive of dementia. Results-Only four of the baseline clinical character istics of Parkinson's disease and neuropsychological variables remaine d independently linked to subsequent development of dementia: the age of onset of Parkinson's disease (>60 years; relative risk (RR) 4.1, 95 % confidence interval (95% CI) 1.8-24.0, p<0.03), the picture completi on subtest of the Wechsler adult intelligence scale (score<10; RR 4.9, 95% CI 1.0-24.1, p<0.02), the interference section of the Stroop test (score<21; RR 3.8, p=0.08), and a verbal fluency task (score<9; RR 2. 7, 95% CI 0.8-9.1, p=0.09). Depressive symptoms and the severity of mo tor impairment were not predictive of dementia. Conclusion-These featu res are different from the neuropsychological characteristics predicti ve of Alzheimers dementia in healthy elderly people (mainly memory and language performance). They are in keeping with the well known specif icity of the impairments in Parkinson's disease for visuospatial abili ties and difficulties in inhibiting irrelevant stimuli, It is postulat ed that the composite nature of the picture completion subtest, involv ing several cognitive abilities impaired in Parkinson's disease, expla ins its sensitivity.