Relationship between age and subtypes of psychotic symptoms in Parkinson's disease

Psychotic symptoms (PS) in Parkinson's disease (PD) usually develop as a side effect of the dopaminergic therapy and consist of hallucinations and delusions. We observed that PD patients who developed delusions tend to be younger than those with hallucinations and we aimed to investigate the validity of this observation.

The medical records of 127 PD patients with PS were reviewed and 76 patients who were on treatment with dopamine agonists with or without levodopa at the time of developing PS were included. Patients were stratified into 3 groups according to the subtypes of PS: patients with solely hallucinations (n = 46), solely delusions (n = 18), and both types (n = 12). The groups were compared with respect to the age-at-onset of PD and PS, duration of PD, Activities of Daily Living (ADL) and motor subscale scores of Unified PD Rating Scale (UPDRS), and levodopa equivalent dose of the dopaminergic agents administered at the time of PS onset.

The mean age-at onset of PD and PS was significantly younger (p = 0.0001) in patients with delusions (49 and 55.9 years) than those with hallucinations (61.9 and 68.9 years). The same parameters were also significantly different (p = 0.002 and p = 0.001, respectively) between the groups of patients with concurrent delusions and hallucinations (51.7 and 57.2 years) and those with only hallucinations. ADL and motor subscale scores were higher in patients with hallucinations (p = 0.016 and p = 0.013) compared with those noted in patients with delusions despite similar disease duration. The mean levodopa equivalent doses of the dopaminergic agents administered at the time of onset of PS did not differ between the groups.

This study supported an association of delusions with younger onset of both PD and psychosis as compared with hallucinations. However, additional factors related to this association remain to be elucidated.