Olfactory Performance & COVID-19 Neuropathy NSF Proposal  

Title: Evaluation of a low cost, psychophysical test to assess olfactory performance as affected by COVID-19 neuropathy

Authors: Ayris Izmirli, Hannah Winter

Project Summary

Overview:

This project is intended to assess olfactory performance as affected by COVID-19 neuropathy through usage of a low cost, psychophysical test. Our participant pool will consist of Drew University students who consent to disclose contraction of the SARS-CoV-2 virus within the past year, as determined by a positive COVID-19 test. “Sniffin sticks” will be utilized to evaluate scent identification. Participants will be asked to distinguish between varying scents that are included in the “Sniffin Stick” kit, which contains 12 different everyday scents (MediSense 2021). We will categorize participants’ level of olfactory sensitivity results as follows: anosmia, total loss of olfactory sensation; hyposmia, partial loss of olfactory sensation; and, normosmia, normal olfactory sensation (Medical Dictionary 2021a, 2021b, 2021c). The primary objective of this study is to demonstrate olfaction alteration post-contraction of the SARS-COv-2 virus, as consistent with the results of previous studies pertaining to this research topic. By replicating the finding that the SARS-CoV-2 virus is capable of altering olfactory perception, we will be able to provide supporting quantitative data that will be beneficial to the field and society. 

Intellectual Merit: 

This research will add to previous knowledge regarding the development of olfactory neuropathy following contraction of the SARS-CoV-2 virus. While COVID-19 is still relatively new, there has been a significant amount of research already conducted about the coronaviruses. By replicating the findings of previous studies, and obtaining supporting qualitative data, we will advance knowledge within this field by demonstrating result consistency, and possibilities for new findings. This information will serve to demonstrate that prior research results surrounding this topic are reliable and can be further built upon in future studies. 

Broader Impacts: 

Although it’s not the most utilized sense, olfaction is a highly useful sense, and also one of the oldest senses as well. Individuals who experience diminished olfaction or loss of olfactory abilities post COVID-19 are commonly also disadvantaged in gustation, which is highly associated with olfaction (Brookes et al., 2020; Hajikhani et al., 2020). This research will increase the database of results consistent with correlated COVID-19 olfactory neuropathy, demonstrating the need for further research to be conducted regarding how to fix this issue. A treatment regarding olfactory neuropathy related to the SARS-CoV-2 virus is unlikely to be researched upon if there is not enough research that supports a significant association between the two factors. This research will support an increased need for funding pertaining to this research topic in general, which will allow for enhancement of individuals’ consequential conditions following COVID-19 to be improved. 

Project Description 

What we want to do:

Plan of work: We will begin carrying out our research study by advertising it to students at Drew University. We will pool students into 2 groups; control, those who haven’t had COVID, & experimental, those who have had COVID, which will allow for later result comparison. 

Design of activities: Sniffin stick kits will be purchased from the U.S. Neurologicals for a price of $325 (MediSense 2021). These kits contain 12 different odors for identification: (1) peppermint; (2) fish; (3) coffee; (4) banana; (5) orange; (6) rose; (7) lemon; (8) pineapple; (9) cinnamon; (10) cloves; (11) leather; and (12) liquorice (MediSense 2021) (Figure 1).

Figure 1: All twelve tubes of Sniffin Sticks and its 12 different flavors.

Figure 2a: Multiple choice with 4 options given to participants.

Figure 2b: Answering pad with 3 columns for left nostril (first column), right nostril (middle column), and both nostrils (third column).

Figure 3: Evaluation pad of scores. Anosmia (dark grey): 0-6 correct answers. Hyposmia (light grey): 6-10 correct answers. Normosmia (white): 10-12 correct answers.

The Sniffin sticks will serve as an odor identification test to assess nasal chemosensory performance (MediSense, 2021). In order of 1 through 12, participants will be exposed to one of the 12 odors individually, and will be asked to identify the odor presented to them by choosing one of four options on a multiple choice sheet (Figure 2a). Olfactory sensitivity levels can be assessed in both nostrils together, or in the left and right nostrils separately, or all 3 in order (Figure 2b). Level of olfactory sensitivity will be determined by the number of correct odor identification responses. On an evaluation pad, anosmia is indicated by the dark grey region suggesting 0-6 correct answers, hyposmia is indicated by the light grey region suggesting 6-10 correct answers, and normosmia is indicated by the white region suggesting 10-12 correct answers (Figure 3) (MediSense 2021).

Where: This research will be conducted in Psychology Research Suite A in the Drew University Hall of Sciences. Data collection will only be conducted in settings where participants and researchers can maintain a sufficient physical distance to limit the possibility of exposure to SARS-CoV-2. Physical distance amongst participants and researchers will additionally ensure that no researcher influenced participant bias occurs, making sure our data is not influenced by any external factors. Instead of principal investigators being in the same room as the participant during the study, participants will be instructed via a camera that is connected to a zoom meeting on how to set up the study themselves from a separate room. 

Why we want to do it:  

Since COVID-19 is still a relatively new topic, there are still a lot of unanswered questions pertaining to it. Significant amounts of research pertaining to SARS-CoV-2 have already been conducted, providing information that answers some of the questions related to the virus. However, there is still a lot unknown, such as how to restore olfactory sensitivity after it is diminished or lost following COVID-19 contraction. While we are not aiming to answer this question specifically with our research, we are hoping to increase the amount of data supporting the topic of COVID-19 induced olfactory neuropathy in hopes that it will eventually lead to further research surrounding this topic and future development of treatments for this condition. 

Relationship of this work to the present state of knowledge in the field: 

Previous research has been conducted to assess the correlation between COVID-19 contraction and consequential olfactory dysfunction. A study published in the American Journal of Neuroradiology used Cranial Magnetic Resonance Imaging (MRI) to observe the olfactory pathogenesis caused by SARS-CoV-2 (Altunisik et al., 2021). Factors analyzed included length of the olfactory tract, volume of the olfactory bulb bilaterally, and depth of the olfactory sulcus. Their findings were consistent with their hypothesis that olfactory dysfunction would be demonstrated in participants who previously had COVID-19. Decreased olfactory bulb volumes and olfactory sulcus depth were observed, and shorter olfactory tract length were identified. While we will not be using MRI technique to carry out our particular study, our research will support the finding of olfactory neuropathy associated with COVID-19 contraction (Altunisik et al., 2021). 

Figure 4: Depicts normal vs. abnormal olfactory bulb structure 

The researchers who conducted the study described above additionally hypothesized a correlation between COVID-19 related anosmia pathophysiology and inflammation of olfactory mucosa and epithelium (Altunisik et al., 2021). However, their results concluded that no significant evidence supported their hypothesis that sinonasal inflammation or obstruction was associated with COVID-19 anosmia. Rather, they found that SARS-CoV-2 virus invades olfactory axons while they are passing through the cribriform plate, causing structural damage to olfactory neurons, which is responsible for COVID-19 anosmia (Altunisik et al., 2021). This was an interesting study because the researchers had not initially hypothesized the result they ended up finding. While the conclusions drawn in this particular study might be more impactful than those we achieve in our study, the results we come to will be beneficial as supportive qualitative data, demonstrating a significant correlation between COVID-19 contraction and olfactory dysfunction. 

Another previously conducted study published in the Journal of Science Translational Medicine observed olfactory neuroepithelium in hamsters who were modeled to have SARS-CoV-2 associated anosmia (de Melo et al., 2021). These researchers were interested in further assessing the neuro invasiveness of SARS-CoV-2, as well as the method in which the virus inhibits the ability to smell. The researchers who conducted this study based their experiment around prior research surrounding observance of SARS-CoV-2 virus in olfactory mucosa during autopsies of patients who died from contracting the virus. Seven Syrian hamsters were intranasally injected with SARS-CoV-2 virus. Viral RNA was detected and isolated from various locations of the hamsters’ brains, including: the olfactory bulb; cerebellum; diencephalon; medulla oblongata; pons; midbrain; and, the cerebral cortex. This information provided lots of insight into the way in which SARS-CoV-2 infects the Central Nervous System. Neuroinflammation at these brain locations was additionally observed, as well as viral presence in the hamsters’ olfactory mucosa (de Melo et al., 2021). 

Figure 5: Demonstrates alterations to olfactory epithelium as caused by SARS-CoV-2 virus, including inflammation and loss of ciliation 

Olfactory functional loss was measured by having the hamsters perform a sucrose-preference test (de Melo et al., 2021). Hamsters who were inoculated with SARS-CoV-2 displayed no preference for sucrose-complemented water compared to regular water. On the other hand, hamsters who were not exposed to SARS-CoV-2 chose to drink from the sucrose-complemented water over the regular water, displaying a clear preference for the sucrose water. These findings demonstrated a significant difference in water preference between hamsters exposed and not exposed to SARS-CoV-2, suggesting olfactory functional loss in hamsters exposed to the virus (de Melo et al., 2021). In comparison to the other research study described above where MRI was used to observe COVID-19 related anosmia pathophysiology, this study suggests that SARS-CoV-2 does cause inflammation of olfactory mucosa, whereas the other study did not draw this same conclusion. The differences among results for each of these studies might suggest that SARS-CoV-2 affects hamsters differently than it does humans, causing a difference in pathophysiology leading to their respective COVID-19 related anosmia. However, the results obtained from both studies are consistent in demonstrating a significant relationship between COVID-19 contraction and consequent olfactory neuropathy. While we will not be conducting a study similar to those described above, we will be hoping to achieve similar results demonstrating a strong correlation between COVID-19 contraction and subsequent decrease in olfactory performance. 

How we will know if we succeed:

Hypothesis A: We will observe a consistency in decreased olfactory performance amongst our experimental participant group who has had SARS-CoV-2 virus in comparison to our control group. 

Hypothesis B: We will observe a difference in olfactory performance amongst experimental participants within our SARS-CoV-2 group; some participants will display diminished sense of olfactory perception following SARS-CoV-2 whereas others will display no sense of olfactory perception at all. 

Hypothesis C: We anticipate that participants who demonstrate decreased olfactory sensitivity will additionally express that they experience diminished gustation in conjunction with it. 

Hypothesis D: The more common odors presented to participants will have a higher identification accuracy rate than odors presented that are not as commonly used or smelt on an everyday basis. 

Hypothesis E: We anticipate that participants who had COVID-19 more recently will display worsened olfactory performance compared to those who had COVID-19 longer ago, and have had more time for their sense of smell to potentially recover in some capacity since their contraction of the virus. 

What benefits would accrue if the project is successful?

If the project is successful, this will enable future researchers to have beneficial qualitative data regarding olfactory loss following contraction of COVID-19, with the use of a low cost test. The results from our research will broaden the range of knowledge pertaining to this topic, allowing for additional future research to be built upon our findings. Having a better understanding of the association between COVID-19 and olfactory neuropathy will assist further research aimed at looking for ways to recover olfactory sensitivity following COVID-19 related loss of it. Additionally, it may broaden the basis of knowledge needed to find a way to prevent diminished or total loss of olfactory sensitivity when individuals contract COVID-19 in the future. 

Broader Impacts:

Since the beginning of the COVID-19 pandemic, there has been worry stemming from the fact that so little is known about the SARS-CoV-2 virus. There has been non-stop, extensive research being done to better understand the way this virus works, however, to this day there is still new information being discovered, such as loss of taste and smell. With this research, we expect to provide potential benefits including gaining a better understanding of sensory processes involved in odor and flavor perception, more specifically with after having contracted COVID-19. Findings will be of interest to researchers and clinicians investigating eating disorders, parosmia, anosmia and phantosmia resulting after contracting COVID-19, effects of the SARS-CoV-2 virus on olfaction and gustation, as well as those investigating the impact of olfactory processes on flavor perception and food and beverage preference and consumption.

In addition, the study will permit the evaluation of a low cost psychophysical test which may increase accessibility to research equipment and methodology and enable future researchers to utilize more cost effective options in many research fields. Although scientists have extensive knowledge of the SARS-CoV-2 virus family, Coronoviridae, there are mutations developing rapidly, and a cost-effective test may be helpful and faster in future research and diagnosis. 

Expected Results:

We expect to observe consistent findings that those in our experimental participant group who have had SARS-CoV-2 will display a worsened sense of perception, and therefore less accurate odor identification scores than those in our control group. We additionally expect to see varying levels of olfactory neuropathy amongst individual participants in our experimental group. We anticipate that some participants will display decreased olfactory sensitivity whereas others will display complete loss instead. This might be influenced by how long ago the participant had COVID-19; we anticipate that we may see some differences in olfactory performance in participants who had COVID-19 more recently compared to participants who had it longer ago. The overall goal of this study is to provide quantitative data to support the conclusions drawn from previous research surrounding this research area. 

References 

Altunisik, E., Baykan, A., Sahin, S., Aydin, E., & Erturk, S. (2021). Quantitative Analysis of the 

Olfactory System in COVID-19: An MR Imaging Study. American Journal of Neuroradiology. Published. https://doi.org/10.3174/ajnr.a7278

Brookes, N. R. G., Fairley, J. W., & Brookes, G. B. (2020). Acute Olfactory Dysfunction—A 

Primary Presentation of COVID-19 Infection. Ear, Nose & Throat Journal, 99(9), 94–98. https://doi.org/10.1177/0145561320940119

de Melo, G. D., Lazarini, F., Levallois, S., Hautefort, C., Michel, V., Larrous, F., Verillaud, B., 

Aparicio, C., Wagner, S., Gheusi, G., Kergoat, L., Kornobis, E., Donati, F., Cokelaer, T., Hervochon, R., Madec, Y., Roze, E., Salmon, D., Bourhy, H., . . . Lledo, P. M. (2021). COVID-19–related anosmia is associated with viral persistence and inflammation in human olfactory epithelium and brain infection in hamsters. Science Translational Medicine, 13(596). https://doi.org/10.1126/scitranslmed.abf8396

Gori, A., Leone, F., Loffredo, L., Cinicola, B. L., Brindisi, G., de Castro, G., Spalice, A., Duse, 

M., & Zicari, A. M. (2020). COVID-19-Related Anosmia: The Olfactory Pathway Hypothesis and Early Intervention. Frontiers in Neurology, 11. https://doi.org/10.3389/fneur.2020.00956

Hajikhani, B., Calcagno, T., Nasiri, M. J., Jamshidi, P., Dadashi, M., Goudarzi, M., Eshraghi, A. 

A., & Mirsaeidi, M. (2020). Olfactory and gustatory dysfunction in COVID‐19 patients: A meta‐analysis study. Physiological Reports, 8(18). https://doi.org/10.14814/phy2.14578

Medical Dictionary. (2021a). Anosmia definition. https://medical-dictionary.thefreedictionary.com/anosmia 

Medical Dictionary. (2021b). Hyposmia definition. https://medical-dictionary.thefreedictionary.com/hyposmia 

Medical Dictionary. (2021c). Normosmia definition. https://medical-dictionary.thefreedictionary.com/normosmia 

MediSense. How to use the Sniffin’ Sticks. (2021, March 14). MediSense | Smelltest.Eu.