Early Parkinson's disease patients on rasagiline present with better odor discrimination

The effects of rasagiline on olfaction in animal studies are convincing. However, apart from various anecdotal patient reports, they could not be reproduced in prospective studies in humans. Cross-sectional data of large patient groups are still missing. The aim of this study was therefore to determine the olfactory function in a broad heterogeneous Parkinson's disease (PD) population with and without rasagiline intake. In this single-center, cross-sectional study 224 PD patients with and without rasagiline (1 mg/day) participated. Seventy-four of them received rasagiline as mono, or adjunct therapy. One-hundred fifty patients were untreated or received PD medication other than rasagiline. Comprehensive olfactory testing was performed for phenyl-ethyl alcohol odor thresholds, odor discrimination, and odor identification. Olfactory function did not differ between the two treatment groups with disease duration up to 29 years. Rasagiline-treated patients with disease duration of less than 8 years, however, presented with significant better odor discrimination abilities compared to PD patients without rasagiline treatment. This effect was no longer evident in patients with longer disease duration and proofed to be independent of age, sex, and medication. Our results may suggest that rasagiline treatment has a positive effect on the processing of olfactory information in early PD.