CORRELATION AMONG OLFACTORY DYSFUNCTION, APATHY AND FATIGUE IN PATIENTS WITH PARKINSON’S DISEASE

Abstract Objectives: Although Parkinson's disease (PD) is usually described as a movement disorder, it exhibits strong associations with non motor symptoms (NMS), including smell and taste dysfunction, neuropsychiatric symptoms, sleep problems and autonomic dysregulation. The olfactory deficit is considered the most common NMS in PD preceding motor symptoms. Aim of this study was first to investigate olfactory function, cognitive impairment, apathy and fatigue in subjects with Parkinson's in relation to healthy controls, and subsequently to analyse the correlation among these NMS in subjects with PD. Methods: One hundred and forty seven subjects (51controls, mean age 65.1 ± 11.8 years and 96 PD subjects with a mean age of 67.8 ± 8.2 years) were enrolled. Olfactory function was evaluated through the Sniffin’ Sticks Extended Test comprised of three different subtests (odor detection threshold, discrimination and identification) and their sum (TDI score). The Montreal Cognitive Assessment (MoCA) test was used to evaluate cognitive impairment. Apathy was examined by self-report version of Starkstein Apathy Scale (SAS) and fatigue was evaluated with the Parkinson’s Disease Fatigue Scale (PFS-16). Results: PD patients showed severe impairment in odor detection threshold, discrimination and identification compared to healthy controls. Moreover, in PD patients apathy score was significantly increased in respect to controls. A negative correlation was observed among all parameters of olfactory function and apathy score. Discussion: Our results identified a greater level of apathy in PD patients affected by severe olfactory loss. These findings suggest that possible common pathways might be involved in these two different NMS. Moreover, the present study confirms that alteration of olfactory parameters, such as odor threshold, identification, discrimination and TDI score, should be related to other NMS, influencing negatively the global quality of life in PD patients.