Thought disorders among non-demented outpatients with Parkinson's disease: prevalence and associated factors

The objectives of the study are to evaluate the prevalence and the associated factors of thought disorders in a large cross-sectional population of non-demented out patients with Parkinson's disease (PD). Four-hundred and nineteen consecutive non-demented PD patients were studied through the DoPaMiP cross-sectional study. Demographic and clinical variables were recorded, including motor and cognitive status, dependency, depressive and anxious symptoms, dysautonomia and sleep disorders. The presence of thought disorders over the past 15 days was assessed by the Unified Parkinson's Disease Rating Scale part I. Patients with and without thought disorders were compared using parametric tests. Logistic regression was applied to significant data. Thought disorders were present in 105 patients (25%) including vivid dreams in 83 (19.8%), benign hallucinations in 17 (4.1%), and hallucinations without insight in 5 (1.2%). No patient had delusion. Patients with thought disorders were more dependent than the others. Thought disorders were associated with longer PD duration, greater UPDRS scores and the presence of motor complications. Conversely, UPDRS tremor sub-score was lower in patients without thought disorders. Thought disorders were also associated with dysautonomia, lower MMSE score, depression and sleep disorders. Logistic regression identified PD duration, lower MMSE score, depressive and dysautonomic signs as independent risk factors. In conclusion, mild thought disorders were present in 25% of non-demented outpatients with PD, but hallucinations were present in 5% only. Thought disorders were associated with PD duration, depressive and dysautonomic symptoms and lower MMSE score.