Neuropsychiatric differences between Parkinson's disease with dementia and Alzheimer's disease

To compare the profile of neuropsychiatric symptoms in patients with Parkinson's disease with dementia (PDD) and patients with Alzheimer's disease (AD).

Cross-sectional survey of a population-based sample of patients with PDD and AD patients matched for age, sex, and Mini-Mental State Examination (MMSE) score.

Patients were diagnosed according to published criteria for PD and AD. The diagnosis of dementia in PD was made according to DSM-III-R, and was based on clinical interview of the patient and a relative, psychometric testing (including MMSE, Dementia Rating Scale and tests assessing memory, executive functions and visuospatial functioning) and physical examination. The Neuropsychiatric Inventory (NPI) was administered to all patients.

One or more psychiatric symptoms was reported in 95% of AD and 83% of PDD patients. Hallucinations were more severe in PD patients, while aberrant motor behavior, agitation, disinhibition, irritability, euphoria, and apathy were more severe in AD. In PDD, apathy was more common in mild Hoehn and Yahr stages, while delusions increased with more severe motor and cognitive disturbances. In PDD, only delusions correlated with the MMSE score.

Neuropsychiatric symptoms are common and severe in patients with PDD, with important implications for the management of these patients. AD and PDD patients have different neuropsychiatric profiles, suggesting different underlying mechanisms. Cognitive impairment, psychopathology, and motor features progress independently in PDD patients