Clinical factors influencing olfactory performance in patients with persistent COVID‐19 smell loss longer than 1 year

Abstract

Abstract Objectives Factors affecting persistence of COVID‐19‐related olfactory dysfunction (OD) remain partially unknown. We aim to evaluate the clinical factors which could influence olfactory performance in patients with persistent COVID‐19‐related smell loss. Methods A retrospective analysis of 100 patients with persistent COVID‐19‐related OD was performed between October 2020 and December 2022 at a single‐center long‐COVID smell clinic. All subjects underwent smell assessment using Sniffin' Sticks (S'S) extended test, nasal endoscopy, nasal airflow evaluation (peak nasal inspiratory flow [PNIF]), allergy test (skin prick test [SPT]) for common aeroallergens, MRI of the head and patient‐reported outcome measures (PROMs—VAS, SF‐36, Short QOD‐NS, SNOT‐22). Based on S'S score, subjects were divided into normosmics (TDI ≥ 30.75) and dysosmics (TDI < 30.75). Results The median age was 42 years and the median length of patient‐reported OD was 1.4 years. 20 patients (20.0%) were normosmic at the time of S'S assessment. Dysosmic patients were found to have significantly lower scores at the SF‐36 health domains for energy/fatigue (p = .0004) and emotional wellbeing (p = .04) when compared to normosmics. A moderate correlation (r = .45–.59) between S'S scores and some PROMs was also demonstrated. At the multivariate analysis higher PNIF scores positively influenced odor threshold (p = .001) while positivity to SPT negatively influenced odor identification (p = .04). Conclusions Impairment of nasal airflow and sensitivity to aeroallergens can negatively affect olfactory performance in COVID‐19‐related OD. Long‐COVID smell loss deeply affects QoL although recovery of olfaction can bring it back to a normal range. Level of Evidence IV.

Keywords

• olfaction
• olfactory disorders
• olfactory test
• quality of life
• smell