Olfaction in LRRK2 Linked Parkinson's Disease: Is It Different from Idiopathic Parkinson's Disease?

Background: Studies on olfaction in LRRK2-associated Parkinson's disease (LRRK2-PD) have yielded variable results. The impact of smell dysfunction upon daily life activities have been rarely assessed in PD. Objective: To characterize the olfactory deficit in LRRK2-PD and its impact on daily life activities. Methods: Twenty-four LRRK2-PD, 40 idiopathic PD (IPD), and 49 age-sex-matched controls were interviewed about olfactory characteristics and the impact of smell on daily life activities. The Barcelona Smell Identification test (BAST-24) and the Spanish-version of the 40-item University of Pennsylvania smell test (UPSIT) were applied. Results: Nineteen (79.2%) LRRK2-PD patients reported subjective smell impairment with a low impact upon daily living activities. UPSIT score was higher in LRRK2-PD than in IPD (22.54 +/- 7.98 vs 18.84 +/- 6.03; p = 0.042). All IPD and 95.8% LRRK2-PD patients had hyposmia/anosmia, assessed by means of the UPSIT. No differences were found between LRRK2-PD and IPD regarding smell detection, memory or forced-choice identification. Conclusion: Most LRRK2-PD patients reported subjective smell impairment and presented hyposmia, according to validated smell tests, with a low impact of the smell dysfunction on daily life activities.