Post-COVID olfactory disorders decrease the quality of life

České info

Post-covidové poruchy čichu zhoršují kvalitu života

Cíl: Porovnat výskyt kvalitativních změn čichu v závislosti na etiologii pomocí cílených otázek. Dalším cílem bylo posoudit dopad ztráty čichu na kvalitu života. Metodika: Dotazník vyplnilo 260 osob s poruchou čichu v letech 2017–2023. Kvalita života související s poruchou čichu byla hodnocena dotazníkem čichové dysfunkce. Tíže poruchy čichu byla zhodnocena Testem parfémovaných fixů (OMT –⁠ Odorized markers rest) a Sniffin’ Sticks testem (vyšetření prahu a 16složkový identifikační test). Zastoupení v etiologických skupinách: covid-19 (n = 58), povirová (n = 66), poúrazová (n = 42), sinonazální (n = 32), idiopatická (n = 42), ostatní (n = 20). Výsledky: Nejčetnější zastoupení kvalitativních poruch čichu je po covidu-19 (n = 58, parosmie 78 %; p < 0,01; fantosmie 60 %; p < 0,01) ve srovnání s ostatními etiologickými skupinami. Pacienti s hyposmií signifikantně četněji udávají parosmie (61 vs. 36 %; p < 0,01) a fantosmie (47 vs. 30 %; p < 0,01) než pacienti s anosmií. Signifikantní rozdíl (p < 0,01) v četnosti negativních tvrzení ukazuje nejvyšší míru utrpení pro pacienty po covidu-19. Nejlépe s poruchou čichu v kladném smyslu (četnost pozitivních tvrzení) vyrovnají respondenti se sinonazální poruchou čichu (p = 0,02). Závěr: Pacienti s poruchou čichu po onemocnění covidem-19 vnímají nejhůře kvalitu života. Zároveň se nejobtížněji vyrovnají s problémy v kladném smyslu. Parosmie a fantosmie se nejčetněji objevuje ve spojení s povirovou poruchou čichu, explicitně po covidu-19. Pacienti, kteří po onemocnění covidem-19 trpí poruchou čichu, vykazují nejnižší kvalitu života a mají velké potíže se zvládáním tohoto stavu.

Klíčová slova:

kvalita života – čich – poruchy čichu

Authors: P. Brothánková ^1,2 ; J. Vodička ^1,2 ; H. Faitlová ¹
Authors place of work: Department of Otorhinolaryngology and Head and Neck Surgery, Pardubice Hospital ¹; Faculty of Health Studies, University of Pardubice ²
Published in the journal: Otorinolaryngol Foniatr, 75, 2026, No. Ahead of Print, pp. 1-6.
Category: Původní práce
doi: https://doi.org/10.48095/ccorl2026-001

Summary

Aim: The objective of this study was to compare the prevalence of qualitative changes in the sense of smell according to etiology using targeted inquiries. Furthermore, the aim was to determine the impact of olfactory dysfunction on the quality of life. Methodology: A total of 260 olfactory dysfunction patients were included. The data were collected over seven years (2017–2023). Olfactory-related quality of life was evaluated using the Questionnaire of Olfactory Dysfunction. Quantitative olfactory performance was assessed using the Odorized Markers Test and Sniffin’ Sticks test. Participants were categorized into etiological groups: COVID-19 (N = 58), postinfectious non-COVID (N = 66), posttraumatic (N = 42), sinonasal (N = 32), idiopathic (N = 42), and other (N = 20). Results: Qualitative olfactory disorders were most prevalent after COVID-19 (N = 58, parosmia 78%; P < 0.01, phantosmia 60%; P < 0.01) compared to other etiological groups. Patients with hyposmia reported significantly higher incidences of parosmia (61 vs. 36%; P < 0.01) and phantosmia (47 vs. 30%; P < 0.01) compared to patients with anosmia. A significant difference (P < 0.01) in the score of negative statements indicates a diminished quality of life of patients after COVID-19. Respondents with sinonasal olfactory disorders showed the most effective coping abilities, and thus, a better quality of life (P = 0.02). Conclusion: Parosmia and phantosmia are most frequently associated with postinfectious olfactory disorders, particularly after COVID-19. Patients who experience olfactory dysfunction after COVID-19 exhibit the lowest quality of life and encounter great difficulty in managing this condition.

Keywords:

Quality of life – olfaction – smell disorders

Introduction

A high percentage of patients with olfactory disorders complain of problems with cooking, food intake, detection of their own body odor, and the occurrence of depression [1, 2]. Persons with olfactory impairment (anosmia and hyposmia) can also concurrently perceive smells distortedly. Thus, they suffer from parosmia (distorted olfactory perception) and/or phantosmia (olfactory perception without odor source) [3]. Most people with persistent parosmia seek treatment and report a decreased quality of life [4]. Among the general symptoms associated with COVID-19, cough, myalgia, and decreased appetite were the most frequently reported. Regarding otorhinolaryngological manifestations, facial pain and nasal obstruction were the most prevalent. A high proportion of patients experienced disturbances with olfactory dysfunction reported in 85.6% and gustatory dysfunction in 88.0% of cases [5]. A significant proportion of patients suffered COVID-19 reported parosmia. It is clear that longer-term follow-up is essential to capture the full extent and burden of olfactory and gustatory dysfunction after COVID-19 infection [6]. Numerous studies have highlighted the detrimental impact of olfactory dysfunction on an individual’s quality of life [1, 2, 7, 8]. The Questionnaire of Olfactory Disorders (QOD), developed and utilized by Frasnelli and Hummel [1], focuses particularly on patients with parosmia, offering subjective insights into olfactory dysfunction and demonstrating high validity, thus serving as a valuable tool in clinical and research settings [1]. This questionnaire assesses the extent to which olfactory disorders affect daily life and the patient‘s ability to cope with the condition. A shortened version of the QOD has been used to evaluate the quality of life in people with chronic rhinosinusitis, which has proven to be userfriendly with high sensitivity and specificity [8]. Similarly, a version tailored for the Chinese population exhibited high reliability [2]. The SNOT-22 questionnaire includes questions about nasal patency and olfactory and taste disorders, which are significant indicators of the quality of life [9]. Fonteyn et al. [10] emphasized the importance of targeted questioning to determine the presence of parosmia and phantosmia, which substantially impair the quality of life. They advocated for the development and use of qualitative questionnaires on olfactory disorders by patients. In addition, a correlation has been observed between the occurrence of parosmia and depressive symptoms [11]. Given the interconnection of parosmia/phantosmia and depression, Croy’s study [12] recommended targeted inquiries about depression symptoms in patients with olfactory disorders, and conversely, targeted inquiries about qualitative olfactory disorders in individuals diagnosed with depression. The primary objectives of our study were:

to define the prevalence of qualitative olfactory disorders over a seven-year period through questionnaire surveys;
to evaluate the quality of life of individuals with olfactory disorders; and
to compare the impact of the etiology of olfactory dysfunction on the quality of life.

Materials and methods

A descriptive, cross-sectional study was conducted. The prospective study was carried out between 2017 and 2023 in the outpatient department for Smell and Taste Disorder Clinic of Otorhinolaryngology and Head and Neck Surgery. Patients were informed about the study procedures and obtaining informed consent was a prerequisite for participation. The research protocol was approved by the Human Research Ethics Committee from our hospital (Protocol number: 503/15.1.2016). All procedures were carried out in accordance with relevant guidelines, regulations, and principles outlined in the Declaration of Helsinki.

Subjects

Participants underwent collection of basic demographic information, medical history, and standardized ear, nose, and throat examination. Subjective taste sensations were recorded before the olfactory evaluation. Quantitative olfactory performance was assessed using the Odorized Markers Test (OMT) and the Sniffin‘ Sticks test. Rhinoepipharyngoscopy was performed using a rigid 30° optic scope. Diagnosis of COVID-19 olfactory disorder was established based on a positive PCR test during the illness or subsequent antibody testing. Participants filled out the questionnaire during visits to a specialized clinic for olfactory and gustatory disorders, with a temporal gap during persistent difficulties. Patients were not approached during quarantine periods.

Questionnaire and olfactory testing

The questionnaire of olfactory dysfunction for individuals with olfactory deficits includes questions pertaining to dietary challenges, as well as social, psychological, and environmental repercussions associated with Olfactory Dysfunction. The questionnaire comprises of 32 items divided into two sections:

negative statements (NS) where lower scores indicate a diminished quality of life; and
positive statements (PS) where lower scores signify enhanced coping abilities, and thus, a better quality of life.

While negative statements evaluated the negative impact of smell loss on the quality of life, positive statements assessed the ability of patients to cope with smell loss. Among these, three items were focused on qualitative disorders of smell (parosmia and phantosmia).

The items are based on a Likert scale ranging from: agree (1 point), rather agree (2 points), rather disagree (3 points), or disagree (4 points). Examples of questions are given in Tab. 1.

Sense of smell was tested using the OMT –⁠ Odorized Markers Test (Centropen® a.s., Czech Republic) and the Sniffin’ Sticks Test (Burghart Messtechnik, Holm, Germany), comprising of a threshold test and a 16-component identification test). There are normal values available for subjects in the Czech population [13]. The distribution of participants according to etiology along with a description of the cohort and results of the olfactory tests, are presented in Tab. 2.

Tab. 1. Examples of questions from the questionnaire.
Tab. 1. Příklady otázek z dotazníku.

Negative statement

The trouble with my sense of smell interferes with my enjoyment of food and drink.

I don’t feel comfortable in the company of other people because I don’t know what I smell like.

Because of the trouble with my sense of smell, I worry that I am constantly exposed to various dangers (e.g. gas, spoiled food).

Positive statement

I can ignore issues concerning my lack of sense of smell in everyday life.

Even though I have a bad sense of smell, I always smell my food before I eat it.

Sometimes I imagine my sense of smell returning.

Statistical analysis

Statistical data analysis was performed using NCSS 2021, v21.0.6. Assessment of the relationships of individual responses of the presence of qualitative disorders with the listed parameters (etiology, gender, olfactory function, taste disorder) tested the hypothesis of independence in the contingency table against the dependence alternative. A chi-square test of independence in a contingency table was used.

For the two groups, the agreement hypothesis was tested against the disagreement alternative. A two-sample t-test was used to compare the results of the questionnaire according to gender and olfactory function and taste disorder. In the case of multiple groups, the hypothesis of agreement was tested against the alternative that at least two groups differ from each other. The non-parametric Kruskal-Wallis analysis of variance with post-hoc Dunn‘s test with Bonferroni modification was used.

Results

There were 260 patients with subjective olfactory dysfunction with a mean age of 51 years (range: 16–86 years), including 164 women (mean age: 51 years) and 96 men (mean age: 50 years). Participants were categorized into etiological groups: COVID-19 (N = 58), postinfectious non-COVID (N = 66), posttraumatic (N = 42), sinonasal (N = 32), idiopathic (N = 42), and other (N = 20).

In the entire cohort (N = 260), 48% of the respondents experienced parosmia, a higher prevalence than phantosmia (38%). Women were more prone to qualitative olfactory disorders compared to men. A significant disparity was observed in the incidence of parosmia between women and men (56 vs 34%; P < 0.01). About 42% of women and 31% of men reported phantosmia (P = 0.06). Patients with hyposmia exhibited significantly higher rates of parosmia (61 vs. 36%; P < 0.01) and phantosmia (47 vs. 30%; P < 0.01) compared to patients with anosmia. Those who subjectively perceived a taste disorder were more likely to report the occurrence of parosmia (54 vs. 41%; P = 0.04), while the difference in phantosmia approached statistical significance (43 vs. 32%; P = 0.06). The most prevalent occurrence of qualitative disorders, classified by etiology, was observed after COVID-19 (N = 58, parosmia 78%; P < 0.01, phantosmia –⁠ 60%; P < 0.01). The frequency of parosmia and phantosmia according to the etiology of olfactory disorders is depicted in Graph 1.

Tab. 2. Distribution of participants by etiology. Cohort description and mean value of the olfactory tests. Tab. 2. Rozdělení respondent podle etiologie. Popis kohorty a průměrné hodnoty bodových zisků čichových testů.
Etiology	Number	Man/woman	Age mean ± SD	Taste disorders yes/no	Anosmia/ hyposmia	OMT (Odourized marker test)	Sniffin’ sticks (identification)	Sniffin’ sticks (threshold)
COVID-19	58	46/12	42.7 (±15.3)	38/20	13/45	6.1	8.4	3.8
postinfectious	66	43/23	55.4 (±12.8)	34/32	42/24	5	7.2	1.9
posttraumatic	42	13/29	44.8 (±14.4)	26/16	38/4	2.9	5	1.2
sinonasal	32	22/10	53.6 (±12.9)	14/18	17/15	5.3	7.4	2.8
idiopathic	42	29/13	57.2 (±16.5)	10/32	14/28	5.1	7.9	2.6
other	20	11/9	49.6 (±22.3)	6/14	8/12	6.6	8	3
Total	260	164/96	50.6 (±16.3)	128/132	132/128	5.1	7.3	2.7

Score of negative statements

The mean scores on negative statements revealed the lowest scores among patients with olfactory disorders after COVID-19 (2.67), followed by posttraumatic (2.74), postinfectious (2.87), sinonasal (2.98), idiopathic (3.24), and other causes (3.47).

A significant difference (P < 0.01) in the negative statement scores indicated that respondents with olfactory impairment after COVID-19 exhibited the lowest scores.

Women reported a poorer quality of life compared to men (2.85 vs. 3.05; P < 0.05). The perception of quality of life was worse among people with anosmia compared to hyposmia (2.83 vs. 3.00; P = 0.02). No significant differences were observed in the change in olfactory impairment over time (improving 2.96; unchanging 2.95; worsening 2.66; fluctuating 2.92; P = 0.47). Respondents who subjectively reported impaired taste exhibited significantly worse quality of life than those who did not report impaired taste (2.69 vs. 3.15; P < 0.01).

Score of positive statements

A significant difference (P = 0.02) revealed that respondents with sinonasal (1.95), postinfectious (2.11), other (2.13), and idiopathic (2.14) olfactory disorders exhibited better coping mechanisms with olfactory disorders. Patients affected by COVID-19 (2.21) experienced greater difficulty in coping with olfactory impairment, while those with post-traumatic olfactory impairment (2.27) reported the most challenges.

No significant differences were observed in the gender-based positive statement score (females 2.13 vs. males 2.18; P = 0.34). Additionally, a positive statement score did not differ significantly depending on the severity of the olfactory disturbance (anosmia 2.18 vs. hyposmia 2.10; P = 0.18). Individuals who reported improvement (1.99) and fluctuation over time (2.10) demonstrated better coping with olfactory impairment compared to those whose sense of smell worsened (2.28) or remained unchanged over time (2.19); P < 0.05. However, no significant differences were observed in positive statements based on subjectively perceived taste disorders (yes 2.20 vs. no 2.09; P = 0.09).

Discussion

The emergence of the COVID-19 pandemic and the subsequent increase in cases of postinfectious olfactory dysfunction, along with manifestations of parosmia, have sparked significant interest leading to the accumulation of new insights. Studies consistently demonstrate negative impacts on mental health, well-being, and nutrition among patients with parosmia. In addition, the pandemic has contributed to a notable increase in phantosmia cases, particularly after recovery from anosmia [14]. At the same time during the COVID-19 pandemic, the significance of not only psychophysical smell tests but also objective olfactory methods grew in the Czech Republic as well. Olfactory event-

-related potentials (OERPs) and trigeminal event-related potentials (TERPs) are electrophysiological techniques that provide the evaluation of changes in olfactory and trigeminal function, which is an objective assessment of the integrity of olfactory pathways. The absence of OERPs is a robust predictor of the presence of olfactory disorders [15, 16].

A study by Elkholi et al. [17] focusing on individuals with olfactory impairment after COVID-19 reported a decrease in the quality of life among 76% of the respondents, with 73.3% reporting a negative effect of olfactory disturbance. Concerns about personal hygiene and decreased food enjoyment were prevalent, where 84.6% reported decreased enjoyment and 66.5% reported worse taste perception. About 23.6% of the respondents reported a positive effect that was reported by 23.6% of respondents who were unaffected by unpleasant odors and did not feel the need to purchase perfume [17].

The results of the study by Martončíková at al. [18] revealed a high incidence of distorted olfactory perception, with parosmia (43.2%) and phantosmia (36.9%) being prevalent, especially among women. These findings are consistent with our results, which also indicate a higher prevalence of these disorders among women [18].

Lerner’s study [4] found that respondents with parosmia exhibited significantly better quantitative olfactory scores, but reported a significantly worse quality of life, as measured by the modified brief QOD-NS. Our study corroborates these findings, showing a higher incidence of parosmia in individuals with hyposmia compared to anosmia and a poorer quality of life among those with qualitative olfactory impairment.

The Questionnaire of Olfactory Disorders (QOD), developed by Frasnelli and Hummel [1], focuses on patients with parosmia and includes sections for negative, positive, and socially desirable statements to improve response credibility. Our study aligns with previous research, indicating that women perceive a lower quality of life compared to men, consistent with higher QOD scores among women. The shortened version of the QOD has been useful in assessing quality of life in various contexts, including chronic rhinosinusitis [8].

Our study encompasses both preand post-COVID periods, allowing a comprehensive assessment of olfactory disorders and their impact on the quality of life over a seven-year period (2017–2023). This allowed for comparison of different etiologies, including changes related to the onset of COVID-19. The study has some limitations. First, patients were surveyed at different time points, which may have introduced inconsistencies into the results. Additionally, the data collection process did not provide precise information regarding the duration of smell disorders. While 70% of participants reported experiencing their smell disorder for a period between one month and two years, 9% reported a duration of one month, 19% reported many years, and 2% reported having the disorder since birth. The study population consisted of patients who sought specialized care from an otolaryngologist, which may have resulted in a higher proportion of individuals with more severe and persistent olfactory dysfunction.

Second, a standardized questionnaire was not used, and validation is recommended for future research. In addition, future research could elaborate account factors as the participants’ safety issues, difficulties with cooking, challenges with food intake, and the occurrence of depression.

Conclusions

In conclusion, postinfectious olfactory disorders, particularly associated with COVID-19, often manifest as parosmia and phantosmia. Patients with hyposmia are significantly more likely to report parosmia and/or phantosmia than patients with anosmia. Patients with COVID-19 experienced greater difficulty in coping with olfactory impairment, while respondents with sinonasal olfactory impairment coped best with their difficulties.

Zdroje

Frasnelli J, Hummel T. Olfactory dysfunction and daily life. Eur Arch Otorhinolaryngol 2005; 262(3): 231 –⁠ 235. Doi: 10.1007/ s00405-004-0796-y.
Yang D, Wang J, Ni D et al.. Reliability and validity of the Chinese version of the Questionnaire of Olfactory Disorders (QOD) when used with patients having olfactory dysfunction. Eur Arch Otorhinolaryngol 2016; 273(10): 3255–3261. Doi: 10.1007/s00405-015-3869-1.
Hernandez AK, Landis BN, Altundag A et al. Ol-factory nomenclature: An orchestrated effort to clarify terms and definitions of dysosmia, anosmia, hyposmia, normosmia, hyperosmia, olfactory intolerance, parosmia, and phantosmia/olfactory hallucination. ORL 2023; 85(6): 312–320. Doi: 10.1159/000530211.
Lerner DK, Garvey KL, Arrighi-Allisan AE et al. Clinical features of parosmia associated with COVID-19 infection. Laryngoscope 2022; 132(3): 633–639. Doi: 10.1002/lary.29982.
Lechien JR, Chiesa-Estomba CM, De Siati DR et al. Olfactory and gustatory dysfunctions as a clinical presentation of mild-to-moderate forms of the coronavirus disease (COVID-19): a multicenter European study. Eur Arch Otorhinolaryngol 2020; 277(8): 2251 –⁠ 2261. Doi: 10.1007/s00405-020-05965-1.
Hopkins C, Surda P, Vaira L et al. Six-month follow-up of self-reported loss of smell during the COVID-19 pandemic. Rhinology 2021; 59(1): 26–31. Doi: 10.4193/Rhin20.544.
Toledano A, Rodríguez G, Martín AM et al. Quality of life in patients with smell loss due to upper respiratory tract infection. Am J Otolaryngol 2011; 32(6): 504 –⁠ 510. Doi: 10.1016/j.amjoto.2010.11.002.
Simopoulos E, Katotomichelakis M, Gouveris H et al. Olfaction-associated quality of life in chronic rhinosinusitis: adaptation and validation of an olfaction-specific questionnaire. Laryngoscope 2012; 122(7): 1450 –⁠ 1454. Doi: 10.1002/lary.23349.
Schalek P, Otruba L, Hahn A. Quality of life in patients with chronic rhinosinusitis: a validation of the Czech version of SNOT-22 questionnaire. Eur Arch Otorhinolaryngol 2010; 267(3): 473–475. Doi: 10.1007/s00405-009-1180-8.
Fonteyn S, Huart C, Deggouj N et al. Nonsinonasal-related olfactory dysfunction: a cohort of 496 patients. Eur Ann Otorhinolaryngol Head Neck Dis 2014; 131(2): 87 –⁠ 91. Doi: 10.1016/j.anorl.2013.03.006.
Hummel T, Landis BN, Hüttenbrink KB. Smell and taste disorders. GMS Curr Top Otorhinolaryngol Head Neck Surg 2011; 10: Doc04. Doi: 10.3205/cto000077.
Croy I, Yarina S, Hummel T. Enhanced parosmia and phantosmia in patients with severe depression. Psychol Med 2013; 43(11): 2460–2464. Doi: 10.1017/S0033291713001773.
Vodička J, Menšíková A, Balatková Z et al. Fyziologické hodnoty čichových testů v české populaci. Otorinolaryngol Foniatr 2011; 60(3): 148–152.
Altundag A. Parosmia and Phantosmia: Managing Quality Disorders. Curr Otorhinolaryngol Rep 2023; 11(1): 19 –⁠ 26. Doi: 10.1007/s40136-023-00441-w.
Holý R, Kalfeřt D, Vašina L et al. Olfactory event-related potentials (OERPs) and trigeminal event-related potentials (TERPs) in subjects after Covid-19 infection: single-center prospective study. J Appl Biomed 2024; 22(3): 149–154. Doi: 10.32725/jab.2024.020.
Holý R, Vorobiov O, Janoušková K et al. Olfactory event-related potentials and trigeminal event-related potentials –⁠ first experience with objective olfactometry in the Czech Republic. Otorinolaryngol Foniatr 2024; 73(3): 134–143. Doi: 10.48095/ccorl2024134.
Elkholi SMA, Abdelwahab MK, Abdelhafeez M. Impact of smell loss on the quality of life and adopted coping strategies in COVID-19 patients. Eur Arch Otorhinolaryngol 2021; 278(9): 3307 –⁠ 3314. Doi: 10.1007/ s00405-020-06575-7.
Martončíková M, Doležal P, Fabianová K et al. Remote psychophysical testing of smell in patients with persistent olfactory dysfunction after COVID-19. Scientific Reports 2023; 13 : 14090. Doi: 10.1038/s41598-023-41395-9.

Conflict of interest statement

The author of this paper declares that she has no conflict of interest in relation to the topic, development, and publication of this paper and that the development and publication of this paper was not supported by any pharmaceutical company. This declaration also applies to all co-authors.