An Observational Study for the Prevalence of Neuropsychiatric Symptom in Parkinson's Disease Dementia

* It is well recognized that the importance of non-motor symptoms of Parkinson's disease during its progression and many patients are suffering from this. The deterioration of cognitive function is especially known as a crucial prognostic factor. According to recently released cohort study, majority of patients go through dementia in advanced Parkinson's disease. * Dementia correlates to decreased cognitive function, and Behavioral and Psychological Symptoms of Dementia (Neuropsychiatric symptom, BPSD) as well. Neuropsychiatric symptom composed of abnormal behavior and psychological symptoms: abnormal behaviors include combativeness, wandering, agitation, akathisia, inappropriate sexual behavior, following caregiver, shouting, cursing, insomnia and binge eating while psychological symptoms include anxiety, depression, hallucination, and illusion. Neuropsychiatric symptom is evaluated depending on information given by caregivers, and symptoms are likely to be temporary or changing constantly. Two thirds of patients is found to have neuropsychiatric symptom when they are diagnosed as dementia, 65 % in nursing home and 70\~90% in advanced dementia states. Neuropsychiatric symptom attributes important role for mortality, mortality, and cause to enter nursing home. * Besides, neuropsychiatric symptom also plays important part as care-giver burden. It gives heavier burden on caregiver rather than on patients, and increases depression and anxiety of caregivers. Specific correlation with patient's neuropsychiatric symptom to burden of caregiver is known as agitation, depression, aggression, repetitive behavior, anxiety, and disinhibition. There are, however, various results related to race, region, subjects, and investigator. * Study on neuropsychiatric symptom in patients with Parkinson's disease dementia has not been thorough yet, and there even has not been any study done on this in Korea yet. * The investigators will study prevalence of neuropsychiatric symptom in PDD patients and burden of caregiver.