Table II. Factors that may contribute to cognitive impairment and dementia in patients with Parkinson's disease (PD). REM, rapid eye movement.

Factors specific to PD

Toxic ity of dopaminergie agents Hallucinations, psychosis, or delirium secondary to antiparkinsonian medications Exacerbation of cognitive dysfunction during medication "off" periods Sleep deprivation (due to sleep fragmentation in PD, REM sleep disorder, vivid nightmares)

Factors common in geriatric patients in general

Medication interactions Use of anticholinergic agents, or agents with high levels of anticholinergic activity Undiagnosed depression or other mood disorder Other psychiatric symptoms (eg, anxiety)