Olfactory Dysfunction Evaluation Is Not Affected by Comorbid Depression in Parkinson's Disease

Abstract

Background: Olfactory function assessment is an important screening tool for Parkinson's disease (PD) diagnosis. It is debated whether olfaction is affected by comorbid depression. We assessed the relationship between depression and olfaction in PD and determined whether depression may limit the usefulness of olfactory testing for PD diagnosis. Methods: Olfaction was evaluated using the Sniffin' Sticks test and the Hyposmia Rating Scale in four groups of subjects: PD patients without depression (n = 30); PD patients with major depression (PDD; n = 30); major depressive disorder (MDD) patients (n = 29); and healthy controls (HCs; n = 30). Results: No differences were found between PD and PDD patients for total Sniffin' Sticks test, threshold, discrimination or identification scores, or in Hyposmia Rating Scale, although both groups differed from HCs and MDD patients (P < 0.05), which, in turn, showed similar olfactory scores. Conclusions: Lack of differences in olfactory impairment between PD and PDD suggest that depression may not contribute to olfactory dysfunction in PD.