Dementia in idiopathic Parkinson's disease. Variables associated with its occurrence in 203 patients.

A series of 203 patients with primary Parkinson's disease treated with L-DOPA, with adequate neurological documentation of mental status at serial intervals during their illness, constitutes the study population. Based on the results of the latest neurological examination, slightly less than one-third (29%) had mental impairment assessed as neurologically significant. Of the eleven clinical variables analysed (Cox regression analysis) for potential influence on the occurrence of an organic mental syndrome, four had a statistically significant effect: (1) the stage of disease at initial neurological examination; (2) the occurrence of acute confusional states; (3) the years of Parkinson's prior to L-DOPA; and (4) the total duration of L-DOPA therapy. The pathogenesis of dementia in this subgroup of Parkinson's disease is discussed.