Determinants of Persistence and Recovery of Chronic COVID19 Chemosensory Dysfunction.

BACKGROUND In 2-4% of patients, COVID19 chemosensory dysfunction (CSD) persists beyond six months, accounting for up to 4 million people in the US. The predictors of persistence and recovery require further exploration. OBJECTIVE To define the predictors of recovery and assess the quality of CSD in registry subjects with self-reported persistent smell and taste dysfunction after COVID19. METHODS COVID19 CSD participants (n=408) from the four major waves of the pandemic completed questionnaires at four time points between 2021 and 2023, assessing demographics, sinonasal symptoms and self-assessed recovery. Objective measurements of smell (UPSIT) and taste (BWETT) were performed on a sub-cohort (n=108). RESULTS In this chronic CSD cohort, the average symptom duration was 24±5 months but 70% those who contracted COVID19 in 2020 have ongoing dysfunction. Phantosmia and dysgeusia were most prevalent in the early waves of COVID19, while most participants reported disrupted ability to distinguish scents and flavors and undulating chemosensory function. Subjects reported low incidence of subjective sinonasal symptoms but high prevalence of sleep and mood disturbance. Cigarette phantom smells were predictive of persistence of CSD. Conversely, self-reported environmental allergies were predictive of recovery and dust mite allergies, specifically, were negative predictors of cigarette phantom smells. Finally, no treatment resolved CSD, but nasal steroids were reported effective by recovered CSD subjects. Objective measures of both smell and taste were significantly reduced in chronic CSD compared to controls. CONCLUSIONS Chronic COVID19 CSD is a syndrome resistant to standard anti-inflammatory therapy. Pre-existing environmental allergies and hypertension predict recovery, while cigarette smoke phantosmia predicts persistence.