The Olfactory Dysfunction of COVID-19

Abstract

Until the coronavirus disease 2019 (COVID-19) pandemic, much of the scientific community and the general public lacked an appreciation of the impact of decreased smell function on everyday life, including the importance of this sensory system for safety, nutrition, and overall quality of life. It is now well established that the SARS-CoV-2 virus inflicts measurable but frequently reversible smell loss during its acute phase. Indeed, in many studies such loss is the most common symptom of COVID-19. Permanent or long-term deficits (i.e., deficits lasting over a year) may occur in up to 30% of those who have been infected, including the development of odor distortions (dysosmias; parosmias). This review presents up-to-date information on the epidemiology, severity, and pathophysiology of COVID-19-related smell dysfunction, including its association with psychological and neurological sequelae.

A Comprehensive Review of COVID-19-Related Olfactory Deficiency: Unraveling Associations with Neurocognitive Disorders and Magnetic Resonance Imaging Findings

“…Substantial damage to olfactory neurons could lead to progressive atrophy of OBs and other structures involved in the olfactory process, thus being responsible for the observed decrease in OBV and OS depth. In other words, while the initial phase of infection may be characterized by an increase in volume due to inflammation, the subsequent phase, marked by persistent neural damage, may manifest with progressive structural thinning [20]. If confirmed, this theory could contribute to explaining variations in OB measurements observed among different studies and underscores the importance of considering the time elapsed since infection in assessing the neurological conditions of COVID-19 patients with OD.…”

“…The two groups were grouped by gender, age, and vaccination dose. Loss of smell was less common in participants infected during Omicron compared to the peak Delta prevalence periods (16.7 vs. 52.7%, OR: 0-17; 95% CI: 0-16-0-19, p < 0.001) [20]. Currently, the exact pathogenesis and molecular mechanisms of OD in COVID-19 are unknown.…”