Parosmia as a predictor of a better olfactory function in COVID-19: a multicentric longitudinal study for upper respiratory tract infections

Abstract

Purpose This study aimed to evaluate the course of olfactory dysfunction [OD] due to upper respiratory tract infections [URTI] especially for COVID-19 [C19] in a multicentric design and to investigate possible predictors for the outcome. Methods In a multicentric study, patients (n = 147, of which 96 were women) with OD due to URTI, including C19 and non-C19 were evaluated at two visits with a standardized medical history and “Sniffin’ Sticks” extended psychophysical testing to examine the course and possible predictors for improvement of olfactory function. Results C19 patients showed better overall olfactory function (p < 0.001) compared to non-C19. Olfactory function (p < 0.001) improved over 3.5 ± 1.2 months in a comparable fashion for C19 and non-C19 comparable over time (p = 0.20) except for a more pronounced improvement of odour threshold (p = 0.03) in C19. C19 patients with parosmia exhibited a higher probability of clinically relevant improvement of odour threshold, a better threshold in the second visit, and tended to have a better TDI-score at the second visit. Further possible predictors for an improving olfactory function were younger age, female gender, and had lower scores in olfactory tests at the first visit. Conclusions Patients with C19 and non-C19 URTI exhibit a similar improvement over 3–4 months except for the odour threshold, with a better TDI in both visits for C19. For C19 a better prognosis in terms of olfactory recovery was found for younger patients with parosmia and lower olfactory scores at the first visit. Still, for many patients with olfactory loss, an improvement that is experienced as complete may only occur over months and possibly years.

Post-COVID-19 patients suffer from chemosensory, trigeminal, and salivary dysfunctions

“…Four out of five patients complained of parosmia, in line with other studies 34 , 60 . These reports are consistent with the theory that parosmia is believed to be a part of the recovery process in patients with impaired olfactory function 61 , 62 . All patients reported the distorted smell and taste to be of an unappealing character.…”

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

“…Similarly, in contrast with previous authors [11][12][13][14]39 we did not find any effect of age on smell recovery. On the other hand, we found a positive significant effect of presence of comorbidities on discrimination scores ( p = .048) which in some aspects corroborates previous results from Chudzik et al 11 who concluded that the risk of developing long-COVID smell loss is greater in people with less comorbidities.…”

“…In another survey on 798 participants Coelho et al 12 showed that age <40 and presence of nasal congestion at time of COVID‐19 infection were predictive of improved rates of smell recovery, while difficulty breathing at time of COVID‐19 infection, and prior head trauma predicted worsened rates of recovery. A positive influence of age (age < 40) on smell recovery was also confirmed by McWilliams et al 13 In a multicentric study on 147 patients, Menzel et al 14 using Sniffin' Sticks (S'S) observed a better prognosis in younger patients with parosmia and lower olfactory scores at the first visit. Conversely, Schwab et al 15 found that parosmia, high severity of OD, and female sex were associated with lower rates of recovery.…”

Subjektive und objektivierte Riech- und Schmeckstörungen aus einer HNO-Post-COVID-19-Sprechstunde

“…Das häufige unangenehme Begleitsymptom einer Parosmie als qualitative Riechstörung wird schon seit Längerem auch als gutes Zeichen einer sich vollziehenden Heilung postviraler quantitativer Riechstörungen diskutiert [11,12]. Jetzt mehren sich die Hinweise, dass das auch auf die Prognose von C19-assoziierten olfaktorischen Funktionsstörungen zutrifft [13,14]…”

“…Das häufige unangenehme Begleitsymptom einer Parosmie als qualitative Riechstörung wird schon seit Längerem auch als gutes Zeichen einer sich vollziehenden Heilung postviraler quantitativer Riechstörungen diskutiert [11,12]. Jetzt mehren sich die Hinweise, dass das auch auf die Prognose von C19-assoziierten olfaktorischen Funktionsstörungen zutrifft [13,14] Aus einer alters-und geschlechtsbezogenen Normwerttabelle [16] ließen sich 3 quantitative Riech-Diagnosen (RD) bestimmen: 1. Ein alters-und geschlechtsbezogen normales Riechvermögen (RDn) lag vor, wenn der SDI zwischen der 95. und einschließlich der 10.…”