Smell as a clinical-marker for functional limitations in multiple sclerosis: A pilot study

Background: Olfactory dysfunction is a common symptom of multiple sclerosis (MS). The questions of whether and to what degree olfactory dysfunction can serve as a clinical marker of MS disability (i.e. cognitive impairments and functional limitations) are not yet answered. The current study aimed to explore associations between olfactory function (i.e. smell identification) with cognitive capacities, functional performance and quality of life (QOL) in persons with MS. Methods: Olfactory function was measured by the University of Pennsylvania Smell Identification Test (UPSIT). Functional ability was assessed by the Actual Reality^TM (AR) task. QOL was assessed by the Multiple Sclerosis Quality of Life-54 (MSQOL-54). Cognition was assessed by the Brief International Cognitive Assessment for MS (BICAMS) in 23 MS patients and 15 matched healthy controls. Results: MS patients had lower UPSIT scores than healthy controls. Worse UPSIT scores were associated with reduced performances on the BICAMS and AR task as well as lower MSQOL-54 scores. Specifically, UPSIT scores were related to MSQOL-54 scores independent of BICAMS composite scores, while the relationship between UPSIT score and AR performance was mediated by BICAMS composite score. Conclusion: This study confirms previous studies which concluded that olfactory function is impaired in MS. Furthermore, olfactory dysfunction is related to limitations in activity performance and QOL. Taken together with previous studies, olfactory function may be considered as a clinical marker related to MS disability. Longitudinal studies are needed to confirm these results.