[Incidence of dementia in Parkinson disease]

The aim of our study was to assess the frequency of dementia in a highly selected (according to diagnostic criteria of Parkinson's disease and other causes of dementia) group of patients.

46 patients (F 18, M 28), mean age--63.9 (39-80) years, with good response to L-Dopa. Besides the neurological examination, all patients underwent CT and psychological tests (Wechsler-Bellevue, Mini Mental and Hamilton test--to exclude severe depression as cognitive problem cause). In the group with dementia thyroxine and cholesterol tests and EEG were performed.

Within the whole group the features of dementia (the index of deterioration in Wechsler test > 25% and/or 23 or less points in Mini-Mental) were recognized in 11 (23.9%) patients. In comparison to the rest of the patients, in the group with dementia the mean age was 8.1 years higher, mean age at onset of the disease was 6.4 years higher, mean time of the disease 1.5 years longer and the severity of the disease measured in Hoehn-Yahr rating scale was 0.76 points higher (2.20 vs 2.96). In the whole group severe depression (> 18 points in Hamilton test) was revealed in 6%, whereas moderate (8-17 points) occurred in 71%.

Older age, later onset of symptoms and more advanced disease are the risk factors of dementia. Other causes--like dementia of Alzheimer's type may be suspected or two distinctive forms of Parkinson's Disease with and without dementia exist.