To investigate the frequency of dementia in patients with Parkinson disease (PD).
Community-based prevalence study.
The study population comprised 220 858 inhabitants from the Rogaland County, Norway.
Almost 400 participants were examined by a neurologist, and 245 were given the diagnosis of PD and included in the study.
Mental functioning was rated with the Mini-Mental State Examination; Gottfries, Bråne, and Steen scale; and the intellectual subscale of the Unified Parkinson's Disease Rating Scale. Criteria from the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised, were applied during a semistructured interview to determine the diagnosis of dementia.
Dementia was found in 67 patients (27.7%). Patients with dementia were older at the time of the study and at onset of PD and had had PD longer than the patients without dementia. Major depression was more common among patients with dementia (23%) than among patients without dementia (2.3%) (ϰ2, P<.001), and patients with dementia were more often institutionalized than those without dementia (62% vs 6%, respectively, ϰ2, P<.001). Atypical neurologic features for idiopathic PD (ie, early occurrence of autonomic failure, symmetrical disease presentation, and only moderate response to a dopamine agonist) were associated with more severe dementia of a higher frequency rate and with lower scores on cognitive rating scales.
Approximately one quarter of the patients with PD had dementia with the motor manifestations of PD. Dementia was associated with depression, institutionalization, older age at onset of PD, and atypical neurologic features.