Motor and non-motor correlates of olfactory dysfunction in Parkinson's disease

Hyposmia is highly prevalent in the motor phase of Parkinson's disease (PD) and is an established pre-motor sign of PD that may precede the onset of motor symptoms by as long as 5 years. The data presented here are part of an ongoing study to determine the relationship of the olfactory deficit in PD with both motor and non-motor features of the disease. The study population so far includes 96 patients with a clinical diagnosis of PD (UK PD Society Brain Bank criteria; mean age 64.9 years; mean disease duration 4.8 years). Olfactory testing was performed using the 40-item UPSIT. We analyzed the relationship between UPSIT scores and measures of motor (disease duration, stage and severity) and non-motor (cognitive function, depression, anxiety and sleep) function. In 60 PD patients, [(123)I]FP-CIT SPECT scans were available to assess the relationship between UPSIT scores and striatal dopamine transporter (DAT) binding. Preliminary analyses revealed correlations of the olfactory deficit in PD with both motor and non-motor features, as well as with striatal DAT binding. These data suggest that the olfactory deficit in PD is not stationary by the time the motor phase is entered, but continues to progress over time. Hyposmia may therefore be useful as a marker of disease progression, at least in the early disease stages.