Olfactory dysfunction is not associated with motor symptom severity in Parkinson’s disease: A cross-sectional study of 1,216 patients

Title : Olfactory dysfunction is not associated with motor symptom severity in Parkinson’s disease: A cross-sectional study of 1,216 patients

Abstract:

Introduction: Hyposmia is an early non-motor feature of Parkinson’s disease (PD), but its relationship with motor symptom severity remains unclear. This study’s objective was to assess the association between olfactory function and motor symptom severity in PD.
Methods: A cross-sectional study of 1,216 patients with confirmed PD from specialist clinics was conducted. Motor severity was assessed using the Unified Parkinson’s Disease Rating Scale (UPDRS) sections I–III, and olfactory function using the University of Pennsylvania Smell Identification Test (UPSIT). Linear and multivariable regression analyses were performed adjusting for age, disease duration, and sex.
Results: In unadjusted analyses, UPSIT scores were negatively associated with UPDRS III (β = −0.156, 95% CI −0.254 to −0.058, p = 0.002; R^2 = 0.008) and UPDRS II (β = −0.069, 95% CI −0.122 to −0.015, p = 0.012; R^2 = 0.005), but not UPDRS I (p = 0.871).
After adjustment for age and disease duration, these associations were no longer significant for UPDRS III (β = −0.066, 95% CI −0.167 to 0.034, p = 0.197; R^2 = 0.037) or UPDRS II (p = 0.099). Further adjustment including sex did not demonstrate significant associations (UPDRS III p = 0.340; UPDRS II p = 0.246; UPDRS I p = 0.364). Effect sizes were small across all models.
Conclusion: Olfactory dysfunction was not independently associated with motor symptom severity after adjustment for confounders. These findings support olfactory impairment as an early, but non-progressive, feature of PD, reinforcing its potential role in early disease detection rather than monitoring progression.

Biography:

Rosa Muijen is a Foundation Year 1 doctor on a Specialised Foundation Programme, with an Academic Neurology rotation. She graduated from Barts and The London School of Medicine and Dentistry with distinctions in every year and a 1^st class intercalated neuroscience degree, during which she was awarded the Best Dissertation Prize. Her previous research includes a publication in Pflüger’s Archiv (2024) investigating optic nerve action potentials with the application of infra-red laser light, reflecting a strong foundation in translational neuroscience. More recently, she has conducted clinical research in Parkinson’s disease in collaboration with the Wolfson Institute of Preventive Medicine, focusing on the relationship between olfactory dysfunction and disease severity. Rosa Muijen has a strong interest in neurodegenerative disease and aims to pursue a career in academic neurology, combining clinical practice with research to improve early diagnosis and patient outcomes.