Background: Cognitive impairments are common in Parkinson's disease (PD). Despite its clinical importance, the development of dementia is still difficult to predict. In this study, we investigated the possible associations between non-motor symptoms and the risk of developing dementia within a 2-year observation period in PD. Methods: A total of 80 patients with PD participated in this study. Nonmotor symptoms (the Nonmotor Symptoms Questionnaire), PD status (Unified Parkinson's Disease Rating Scale), depression (Geriatric d Depression Scale or Montgomery-Asberg Depression Scale), stereopsis and severity of nonmotor symptoms (Non-motor symptoms scale) were assessed. Global cognitive function (Mini-Mental State Examination) were evaluated at baseline and 2 years later. Results: Presence of depression, vivid dreaming, REM sleep behavior disorders, hyposmia, abnormal stereopsis, non-smoking and postural instability/ gait disturbance phenotype were associated with a significantly more rapid decline of Mini-Mental State Examination. Logistic regression analyses demonstrated that depression (odds ratio = 13.895), abnormal stereopsis (odds ratio = 10.729), vivid dreaming (odds ratio = 4.16), REM sleep behavior disorders (odds ratio = 5.353) and hyposmia (odds ratio = 4.911) were significant independent predictors of dementia risk within 2 years. Postural instability/ gait disturbance phenotype and age >62 years were also independent predictors of dementia risk (odd ratio = 38.333, odds ratio = 10.625). Conclusions: We suggest that depression, vivid dreaming, REM sleep behavior disorders, hyposmia and abnormal stereopsis are closely associated with cognitive decline, and that presence of these nonmotor symptoms predict the subsequent development of Parkinson's disease dementia. Résultats: La présence de dépression, de rêves intenses et troublants, de troubles du comportement du sommeil paradoxal, d'hyposmie, d'anomalies de la stéréopsie, le fait d'être non-fumeur et l'instabilité posturale/la démarche anormale étaient associés à un déclin significativement plus rapide du score au Mini-Mental. Les analyses de régression logistique ont montré que la dépression (rapport de cotes (RC) = 13,895), la stéréopsie anormale (RC = 10,729), les rêves intenses et troublants (RC = 4,16), les troubles du comportement du sommeil paradoxal (RC = 5,353) et l'hyposmie (RC = 4,911) prédisaient de façon indépendante le risque de démence au cours des 2 prochaines années. Une instabilité posturale/une démarche anormale et un âge supérieur à 62 ans prédisaient de façon indépendante le risque de démence (RC = 38,333, RC = 10,625). Conclusions: Nous proposons que la dépression, les rêves intenses et troublants, les perturbations du comportement du sommeil paradoxal, l'hyposmie et la stéréopsie anormale sont étroitement associés au déclin cognitif et que la présence de ces symptômes non moteurs prédit l'apparition subséquente de la démence dans la maladie de Parkinson.
