Comparison of Olfactory Thresholds between Elderly with Parkinson Disease and Controls

Introduction: Olfactory dysfunction is an early warning and most common symptom of Parkinson's disease (PD). It is a promising marker mainly at the early stage of the disease for PD. The purpose of the survey was to evaluate the deficits in odor detection in Elderly with PD. We hypothesized that trigeminal sensitivity dysfunction would be less important than olfactory sensitivity impairment in elderly with PD and could improve diagnostic accuracy. Experimental procedure: Olfactory detection thresholds to Phenyl ethyl alcohol (PEA) [activating only the olfactory system] and n- Butanol (BUT) [activating both olfactory and trigeminal systems], were determined in twenty four patients with PD aged over 65 years old [mean age: 75 +/-4.5 years, range: 70-86 years] and in twenty-four healthy controls who were matched for age and gender [mean age: 73 +/-7.1 years, range: 65- 84 years]. The study also included neuropsychological evaluations and stage of PD estimations. Results: Results show a trend towards an impaired olfactory (CN I) detection sensitivity in relation to PEA thresholds in patients with PD compared to controls independently of age and stage of PD, although no significant difference was observed. Furthermore, no significant difference was observed for BUT thresholds between PD’s patients and controls. PEA and BUT thresholds were significantly correlated in both patients with PD and controls. Conclusion: These findings suggest that the olfactory senescence and decreased detection threshold in elderly (both patients with PD and controls) may influence our results by reducing detection olfactory threshold differential between the two groups, contrary to previous findings in young adults with PD and controls. Trigeminal sensitivity seems to be preserved in Elderly with PD. Future investigations should focus on odorants with higher properties to highlight a potential difference between the two groups.