Hallucinations, sleep fragmentation, and altered dream phenomena in Parkinson's disease

In a series of consecutively randomized outpatients who had Parkinson's disease (PD), we examined the association of three behaviors: sleep fragmentation, altered dream phenomena, and hallucinations/illusions. Using a log-linear model methodology, we tested the independence of each behavior. Sixty-two percent of the subjects had sleep fragmentation, 48% had altered dream phenomena, and 26% had hallucinations/illusions. Eighty-two percent of the patients with hallucinations/illusions experienced some form of sleep disorder. The three phenomena were not independent. The interaction between sleep fragmentation and altered dream phenomena was strongly statistically significant. Likewise, a significant interaction existed between altered dream phenomena and hallucinations/illusions. No interaction occurred between sleep fragmentation and hallucinations/illusions. Sleep fragmentation, altered dream phenomena, and hallucinations/illusions in PD should be considered distinct but often overlapping behaviors. The close association between altered dream phenomena and hallucinations suggests that therapeutic interventions aimed at diminishing dream-related activities may have a specific positive impact on hallucinatory behavior.