Age-related influences on the clinical characteristics of new-onset hallucinations in Parkinson's disease patients.

The objective of this study was to determine the demographic influences on the sensory characteristics (pure visual vs. nonvisual or mixed visual/nonvisual) of new-onset hallucinations in Parkinson's disease (PD). We utilized 6-year longitudinal interview data from 60 PD patients who had never hallucinated at baseline and reinterviewed them at 6, 18, 48, and 72 months to assess the presence and type of hallucination that developed as the first form of hallucination. We analyzed data by Generalized Estimating Equations methods and by nonparametric tests. Over 6 years, 37 of 60 patients developed hallucinations, and the first hallucinations were pure visual in 18, pure nonvisual in 9, and mixed visual/nonvisual in 10. At the time of first onset of hallucinations, patients whose hallucinations were nonvisual or mixed were significantly older than those with purely visual hallucinations (mean age, 69.8+/-8.3 vs. 61.9+/-10.6; P=0.031). PD duration in the two groups, however, was statistically comparable (9.6+/-4.4 vs. 12.9+/-8.6 years). Though classically described as visual, hallucinations in PD frequently involve other sensory modalities. Age-related disinhibition may facilitate wider cortical activation in PD and potentiate aberrant signaling that invokes other types of hallucinations besides the classic visual forms.