Factors associated with relevant olfactory recovery after olfactory training: a retrospective study including 601 participants

Age-related differences in olfactory training outcomes: A prospective cohort study

INTRODUCTION

While olfactory function decreases with age, it is unknown how age affects olfactory training (OT) efficacy. This study compared OT in two cohorts of subjects: aged ≤50 (younger cohort) and aged 51+ (older cohort) with olfactory dysfunction (OD) primarily from COVID-19 infection.

METHODS

Subjects with OD primarily secondary to COVID-19 infection were prospectively recruited and enrolled into an OT registry. Baseline data were collected and they were provided with a training kit and asked to complete OT at home twice daily for 6 months. Participants were asked to follow-up at 3 and 6 months during training for olfactory testing and quality-of-life surveys (Sino-Nasal Outcomes Test-22 [SNOT-22] and Questionnaire of Olfactory Disorders Negative Statements [QoD-NS]).

RESULTS

Fifty-six participants completed OT (younger cohort: n = 26, older cohort: n = 30). There were no significant differences between cohorts' Affordable Rapid Olfactory Measurement Array (AROMA), QoD-NS, or SNOT-22 scores at any time point. Both cohorts showed significant AROMA score improvement of more than 16 points from baseline to 3 months (younger cohort: p = 0.001; older cohort: p = 0.008). The younger cohort had significant improvements in QoD-NS (p = 0.008) and SNOT-22 (p = 0.042) between baseline and 3 months while the older cohort improved from 3 to 6 months (QoD-NS: p = 0.027, SNOT-22: p = 0.049).

CONCLUSION

Both cohorts demonstrated similar significant improvement in olfactory function after 3 months of OT. The timeline of subjective improvement was different between cohorts, with younger patients experiencing earlier improvement.

Four odorants for olfactory training are enough: a pilot study

BACKGROUND

 Olfactory training (OT) is commonly used for the treatment of olfactory disorders. Nevertheless, there is an ongoing debate about the most effective OT regimen. We aimed to compare the effects of OT with 7 items (rose, lemon, eucalyptus, cloves, stewed apple, balm, mint) to 4-item-OT (rose, lemon, eucalyptus, cloves) over 3 months. Methods: Participants were 40 patients with olfactory dysfunction receiving 4-item-OT or 7-item-OT and 60 gender- and age-matched individuals with normal sense of smell receiving no OT, 4-item-OT, or 7-item-OT. Before and after the OT we assessed n-butanol odor thresholds, discrimination, and identification (TDI score), additionalthresholds for (R)-(-)-carvone, β-damascenone, salicyclic acid benzylester, the degree of phantosmia and parosmia, cognitive function, and ratings of olfactory function. Results: In both patient groups, the TDI score increased with the use of OT, regardless of the number of odors used (p < 0.001; 3.48 ± 4.21 and lower than control groups). The clinically significant increase of 5.5 points in TDI score correlated with change of ratings of parosmia (r 0.62; p < 0.01) and with ratings of olfactory dysfunction (r = 0.51; p < 0.05).

CONCLUSION

 Concluding, OT over a 3-months period with 4 or 7 odors appears to produce similar results, although the sample size has to be considered.

The olfactory diary: Tracking awareness and consciousness of the sense of smell throughout the day

Objectives

The aim of the present study was to follow the daily course of patients with olfactory dysfunction and healthy controls and to assess (i) how many times a day, (ii) at which time, and (iii) in which aspect of daily life participants are conscious about their sense of smell.

Methods

In this longitudinal study, 49 patients with smell loss and 30 healthy participants were enrolled. Olfactory function was assessed using the Sniffin' Sticks. All participants received paper diaries designed for a 14-day period, featuring 12 rows representing 12 daily hours and six columns for various daily life aspects. They were instructed to mark their awareness of smell by indicating the relevant row and column in the diary. Following the return of the diaries, a second olfactory test was conducted within the patient group.

Results

On average, patients were consciously aware of their sense of smell around 8 times daily, while healthy participants noted it about 6.5 times a day. Both groups primarily focused on their sense of smell during activities related to "eating," followed by considerations in "social life" and "personal hygiene." Interestingly, distinct patterns emerged: patients peaked in awareness at 8 a.m. and 7 p.m., whereas healthy individuals showed peaks at 6 a.m., 12 p.m., and 7 p.m. Despite regular diary use, we observed no improvement in patients' olfactory function or related quality of life.

Conclusion

The olfactory diary is a valuable tool unveiling individual smell awareness patterns in patients with smell loss, aiding in counseling and patient management.

Level of Evidence

4.

Eating behavior in patients with smell loss

Background

The objective of this study was to determine how clinical characteristics and validated quality of life (QoL)-measures are associated with eating behavior in patients with olfactory dysfunction (OD).

Methods

For this cross-sectional study, 150 OD patients of different causes were retrospectively recruited. Olfactory function was measured using the Sniffin’ Sticks (TDI), while olfactory-related QoL was evaluated with the Questionnaire of OD negative and positive statements (QOD-NS and QOD-PS). The importance of olfaction was measured using the Importance of Olfaction Questionnaire (IOQ). The Dutch Eating Behavior Questionnaire (DEBQ) assessed eating behavior based on emotional, external, and restrained eating. Associations were sought between eating behavior metrics (as dependent variables) with clinical characteristics and olfactory-related outcome measures.

Results

Emotional, external, and restrained eating behavior deviating from normative standards were reported in 54%, 71.3%, and 68% of patients, respectively. Multivariate regression modeling revealed that emotional eating was associated with age (ß = –0.227, p = 0.032), the body mass index (BMI, ß = 0.253, p = 0.005), the TDI (ß = 0.190, p = 0.046), and the QOD-NS (ß = 0.203, p = 0.049). External eating was associated with OD duration (ß = 0.291, p = 0.005), the TDI (ß = 0.225, p = 0.018), the QOD-PS (ß = –0.282, p = 0.008), and the IOQ (ß = 0.277, p = 0.004). Restrained eating was associated with age (ß = 0.216, p = 0.033), the BMI (ß = 0.257, p = 0.003), male gender (ß = –0.263, p = 0.002), and the IOQ (ß = 0.332, p &lt; 0.001).

Conclusion

Clinical characteristics and olfactory outcome measures differentially impact eating styles in OD patients. Our study’s results highlight the importance of considering unfavorable changes in eating behavior during clinical counseling.

Novel Therapies in Olfactory Disorders

Purpose of Review

To summarize and critically review the recent literature on novel treatments for olfactory disorders (OD).

Recent Findings

Emerging therapies in the management of OD include multiple vitamins and supplements, biologics, neuromodulators, and intranasal agents. There is also an active investigation into treatments that harness the neuroregenerative properties of the olfactory epithelium, such as platelet-rich plasma and stem cell transplantation.

Summary

Successful management of OD is multimodal and tailored to the underlying etiology. As the findings of further investigations accrue, the management of OD will undoubtedly continue to be advanced and refined, and likely harness the intrinsic neuroregenerative properties of the olfactory system.

Olfactory training - Thirteen years of research reviewed

The sense of smell is interrelated with psychosocial functioning. Olfactory disorders often decrease quality of life but treatment options for people with olfactory loss are limited. Additionally, olfactory loss accompanies and precedes psychiatric and neurodegenerative diseases. Regular, systematic exposure to a set of odors, i.e., olfactory training (OT) has been offered for rehabilitation of the sense of smell in clinical practice. As signals from the olfactory bulb are directly projected to the limbic system it has been also debated whether OT might benefit psychological functioning, i.e., mitigate cognitive deterioration or improve emotional processing. In this review we synthesize key findings on OT utility in the clinical practice and highlight the molecular, cellular, and neuroanatomical changes accompanying olfactory recovery in people with smell loss as well as in experimental animal models. We discuss how OT and its modifications have been used in interventions aiming to support cognitive functions and improve well-being. We delineate main methodological challenges in research on OT and suggest areas requiring further scientific attention.

[Guideline S1: Long COVID: Diagnostics and treatment strategies]

This guideline comprises the state of science at the time of the editorial deadline. In view of the high turnover of knowledge the guideline is designed as a living guideline. The main objective was to provide a tool for the use in primary care, being considered well suited as a first point of entry and for the provision of care. The guideline gives recommendations on the differential diagnosis of symptoms following SARS-CoV‑2 infection, on their therapeutic options, as well as for guidance and care of the patients concerned. It also offers advice concerning return to daily life and rehabilitation. Long COVID being a very variable condition, we chose an interdisciplinary approach.

Effects of olfactory training on posttraumatic olfactory dysfunction: a systematic review and meta-analysis

BACKGROUND

Posttraumatic olfactory dysfunction is a clinical challenge due to refractory characteristics and limited therapeutic options. Olfactory training has been proved to be effective for olfactory dysfunction with varied etiologies. We pooled existing studies to evaluate the effects of olfactory training in patients with posttraumatic olfactory dysfunction.

METHODS

A systematic literature review using PubMed, Embase, Cochrane Library, and Web of Science was conducted to identify studies assessing olfactory change in patients with posttraumatic olfactory dysfunction after olfactory training.

RESULTS

Of the initial 812 abstracts reviewed, 13 full-text articles were included. Clinically significant results after olfactory training were defined as an improvement of threshold, discrimination, and identification (TDI) score ≥6 or University of Pennsylvania Smell Identification Test (UPSIT) score ≥4. Six studies were included in the meta-analysis, 36.31% (95% confidence interval [CI], 0.28 to 0.45) of posttraumatic patients would achieve clinically significant results after olfactory training with a mean increase of TDI score of 4.61.

CONCLUSION

Olfactory training might be a promising modality for the treatment of posttraumatic olfactory dysfunction. More high-quality studies with controls are needed to clarify the effect of olfactory training on total olfactory performance and subcomponents of olfaction.

Clinical Implications of Psychophysical Olfactory Testing: Assessment, Diagnosis, and Treatment Outcome

Purpose of Review

Olfactory dysfunction dramatically impairs quality of life with a prevalence of 20% in the general adult population. Psychophysical olfactory testing has been widely used to evaluate the ability to smell due to its validated utility and feasibility in clinic. This review summarizes the current literature regarding psychophysical olfactory testing and the clinical relevance of the olfactory testing with different components. Furthermore, the review highlights the diagnosis and treatment value of olfactory subtests in patients with olfactory dysfunction.

Recent Findings

With the accumulation of studies of psychophysical olfactory testing in olfactory disorders, the clinical relevance of olfactory testing with different components is expanding. Different olfactory domains present with distinct olfactory processing and cortical activity. Psychophysical assessment of olfaction with three domains reveals different levels of olfactory processing and might assist with analyzing the pathophysiologic mechanism of the various olfactory disorders. Furthermore, olfactory thresholds provided the largest amount of non-redundant information to the olfactory diagnosis. Sinonasal olfactory dysfunction and non-sinonasal-related olfactory dysfunction are emerging classifications of smell disorders with certain characteristics of olfactory impairment and different responses to the therapy including steroids, sinus surgery, and olfactory training.

Summary

These recent advancements should promote the understanding of psychophysical olfactory testing, the association between individual subcomponents and neurophysiological processes, and pave the way for precision assessment and treatment of the olfactory dysfunction.

Assessment of odor hedonic perception: the Sniffin' sticks parosmia test (SSParoT)

Qualitative olfactory dysfunction is characterized as distorted odor perception and can have a profound effect on quality of life of affected individuals. Parosmia and phantosmia represent the two main subgroups of qualitative impairment and are currently diagnosed based on patient history only. We have developed a test method which measures qualitative olfactory function based on the odors of the Sniffin' Sticks Identification subtest. The newly developed test is called Sniffin' Sticks Parosmia Test (SSParoT). SSParoT uses hedonic estimates of two oppositely valenced odors (pleasant and unpleasant) to assess hedonic range (HR) and hedonic direction (HD), which represent qualitative olfactory perception. HR is defined as the perceivable hedonic distance between two oppositely valenced odors, while HD serves as an indicator for overall hedonic perception of odors. This multicenter study enrolled a total of 162 normosmic subjects in four consecutive experiments. Cluster analysis was used to group odors from the 16-item Sniffin' Sticks Identification test and 24-additional odors into clusters with distinct hedonic properties. Eleven odor pairs were found to be suitable for estimation of HR and HD. Analysis showed agreement between test-retest sessions for all odor pairs. SSparoT might emerge as a valuable tool to assess qualitative olfactory function in health and disease.