PASC Cardiac Symptoms: Chronic Anosmia Following COVID-19 Illness

Please Note: The information below is intended for healthcare professionals, specifically primary care providers. These are not meant to be guidelines or supplant individual provider discretion in the management of PASC, as evidence-based consensus guidelines for the diagnosis of management of this new disease do not exist currently. The following represents the expert opinions of an interprofessional group that is appraising emerging evidence and should be interpreted as recommendations and clinical guidance rather than the standard of care.

PASC Cardiac Symptoms: Chronic Anosmia Following COVID-19 Illness

Written June 28, 2021 by: Faith Noah, MS3, Matthew Seghers, MS3, W. Michael Brode, MD

Loss of smell and taste (anosmia and ageusia, respectively) occur in approximately 50% of patients during their initial COVID-19 illness.1,2 These sensory deficits persist at 6 months in approximately 15-25% of patients3 likely secondary to peripheral inflammation.

The overall prognosis for chronic anosmia is excellent, with studies showing > 95% of patients recovering at 12 months.4,5

Olfactory training is the mainstay of treatment, which patients can do independently using the website to guide them. Adding nasal corticosteroids (mometasone furoate 100 mcg twice daily is the best studied) in addition to olfactory training may have a small benefit in severe cases, but for most patients is not necessary.6

The incidence of anosmia during acute COVID-19 illness varies from 34-68% and is thought to be more common in younger patients and women.2,7 Anosmia typically appears 4-5 days after appearance of other infectious symptoms, and for the majority of patients, it resolves after 1 week.8 Altered smell and taste (parosmia, dysgeusia) has also been widely reported during the recovery phase of illness.3

A metanalysis of chronic post-COVID-19 symptoms estimated that anosmia can persist at 6 months in 24% of affected patients and ageusia persisted in 16% of patients.3

  • True prevalence of anosmia could be higher than reported, as studies have shown more than half of COVID-19 patients who were not aware of their anosmia until formal testing.2 Similarly, recovery rates may also be underestimated because patients under-appreciate return of normosmia until objective testing4 demonstrates their recovery.

The nasal cavity can be the first gateway for infection with the SARS-CoV-2 virus, infecting nasal mucosa’s goblet cells and ciliated cells. There is a high concentration of angiotensin-converting enzyme 2 receptor in the nares through which SARS-CoV-2 enters the body.7

  • The underlying pathophysiology is uncertain, but it appears that the virus does not directly destroy olfactory neurons and is a peripheral phenomenon. Instead, there appears to be chronic inflammation or destruction of supporting cells and neuroepithelium, which can regrow. This proposed mechanism potentially explains how long-term anosmia can persist even after the infection has resolved.8,9

Anosmia is diagnosed by olfactory function test, an objective assessment tool that commonly measures odor threshold of detection, odor discrimination, and odor identification.2,7 In the primary care setting, this is not widely available, so the history should focus on the types of smells patient can no longer detect, whether it is absent or diminished, or change in quality of typical smells (parosmia).

Physical exam should evaluate for nasal polyps or chronic sinusitis, which may indicate another etiology of the symptoms or impeding recovery if unaddressed.

Imaging is NOT recommended.

Consider treatment after symptoms persist for more than 2 weeks, although the prognosis is excellent with studies showing > 95% of patients recovering at 12 months.4,5

The mainstay of treatment is olfactory training. This can be done independently by the patient at home using a self-made “smell kit” or purchasing one online for less than $40. We recommend the website for free self-guidance for patients.

Olfactory training has been demonstrated to improve smell sensation in post-infectious anosmic individuals, and it includes:

  • Deliberately sniffing odors for 20 seconds at least twice per day for at least 3 months or longer

Evidence for the use of nasal corticosteroids is mixed, with some studies showing no benefit when used in combination with olfactory retraining and other trials showing a small benefit at 4 weeks in severe cases.6

  • Mometasone furoate 100 mcg twice daily for 4 weeks is the best studied nasal spray regimen, although fluticasone and betamethasone are reasonable alternatives if they are more affordable.

Intranasal sodium citrate, intranasal vitamin A, and systemic omega-3 are hypothesized to aid olfactory function but have not yet been proven effective in post-COVID-19 patients.7 We recommend against these experimental treatments, especially given the overall favorable prognosis of this condition.

1. Saniasiaya J, Islam MA, Abdullah B. Prevalence of Olfactory Dysfunction in Coronavirus Disease 2019 (COVID-19): A Meta-analysis of 27,492 Patients. The Laryngoscope. 2021;131(4):865-878. doi:10.1002/lary.29286

2. Meng X, Deng Y, Dai Z, Meng Z. COVID-19 and anosmia: A review based on up-to-date knowledge. Am J Otolaryngol. 2020;41(5):102581. doi:10.1016/j.amjoto.2020.102581

3. Nasserie T, Hittle M, Goodman SN. Assessment of the Frequency and Variety of Persistent Symptoms Among Patients With COVID-19: A Systematic Review. JAMA Netw Open. 2021;4(5):e2111417. doi:10.1001/jamanetworkopen.2021.11417

4. Renaud M, Thibault C, Le Normand F, et al. Clinical Outcomes for Patients With Anosmia 1 Year After COVID-19 Diagnosis. JAMA Netw Open. 2021;4(6):e2115352. doi:10.1001/jamanetworkopen.2021.15352

5. Lechien JR, Chiesa‐Estomba CM, Beckers E, et al. Prevalence and 6‐month recovery of olfactory dysfunction: a multicentre study of 1363 COVID‐19 patients. J Intern Med. Published online January 5, 2021:joim.13209. doi:10.1111/joim.13209

6. Kasiri H, Rouhani N, Salehifar E, Ghazaeian M, Fallah S. Mometasone furoate nasal spray in the treatment of patients with COVID-19 olfactory dysfunction: A randomized, double blind clinical trial. Int Immunopharmacol. 2021;98:107871. doi:10.1016/j.intimp.2021.107871

7. Whitcroft KL, Hummel T. Olfactory Dysfunction in COVID-19: Diagnosis and Management. JAMA. 2020;323(24):2512-2514. doi:10.1001/jama.2020.8391

8. Santos REA, da Silva MG, do Monte Silva MCB, et al. Onset and duration of symptoms of loss of smell/taste in patients with COVID-19: A systematic review. Am J Otolaryngol. 2021;42(2):102889. doi:10.1016/j.amjoto.2020.102889

9. Butowt R, von Bartheld CS. Anosmia in COVID-19: Underlying Mechanisms and Assessment of an Olfactory Route to Brain Infection. The Neuroscientist. Published online September 11, 2020:1073858420956905. doi:10.1177/1073858420956905