The association between cognitive impairment and neuropsychiatric symptoms in patients with Parkinson's disease dementia

Background: Neuropsychiatric symptoms (NPS) are common in patients with dementia associated with Parkinson's disease (PDD). The relationship between cognition and NPS in PDD has not been well studied. Methods: Patients diagnosed with PDD were assessed for cognitive function and NPS. The instruments used were the Neuropsychiatric Inventory (NPI), Mini-Mental State Examination (MMSE), and semantic verbal fluency according to the recommendation of the Movement Disorder Society Task Force. Results: We evaluated 127 PDD patients (76 males/51 females; mean age 77 +/- 6.3 years). Their mean MMSE score was 17 +/- 6.5 and the mean NPI score was 19 +/- 20.4. The most prevalent NPI items were anxiety (57.5%), sleep problems (53.5%), and apathy (52.0%). Principal component factor analysis revealed that 12 items formed three factors, namely mood and psychosis (delusion, hallucination, agitation, depression, anxiety, apathy, and irritability), vegetative (sleep and appetite problems), and frontal (euphoria, disinhibition, and aberrant motor behavior). Symptoms of hallucination were significantly associated with MMSE score, even after controlling for the confounding variables. Conclusion: NPS are common and diverse among patients with PDD. Three specific subgroups of NPS were identified. Hallucination was significantly correlated with cognitive impairment, and could be a predictor of cognition in PDD patients.