COVID-19 'Loss of Smell' Decreased with Emerging Variants [Reading Science]

Nature Reports on US NIH Research Results....Treatment Methods Also Under Development

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[Asia Economy Reporter Kim Bong-su] The number of people experiencing loss of smell and taste symptoms caused by COVID-19 has been gradually decreasing as new variants of the virus emerge. Although some patients suffer for nearly a year, treatments using steroids and plasma are making progress, offering hope.

According to the international academic journal Nature on the 9th (local time), last month the U.S. National Institutes of Health (NIH) examined the medical records of 616,318 COVID-19 patients and discovered this fact. Specifically, 50% of patients infected with the Alpha variant of the COVID-19 virus experienced olfactory and gustatory disorders, but this rate dropped to 44% with the Delta variant and sharply declined to 17% with the recent Omicron variant.

However, even so, the issue of loss of smell and taste among COVID-19 patients remains serious. In another NIH study conducted in December last year, 46% of 100 mild COVID-19 patients reported experiencing chemical sensory disorders, and 7% said they suffered from complete or partial loss of smell for nearly a year. Considering that approximately 500 million people worldwide have been infected with COVID-19, tens of millions have suffered from chemical sensory disorders. The inability to perceive smell or taste may seem simple, but it is a significant stress-inducing disability for those affected.

Scientists discovered early in the COVID-19 pandemic that the virus destroys sustentacular cells in the nose, which provide nutrients and support to the brain cells responsible for detecting odors. In fact, a research team at Columbia University in New York examined the noses of deceased COVID-19 patients and confirmed that the number of odor-detecting cells was significantly lower than usual. In March, a study in the UK involving about 400 people who underwent brain scans before and after COVID-19 infection revealed that the brains of infected individuals showed shrinkage and other changes compared to normal cases.

However, there is hope. Currently, the best treatment to restore olfactory cell function is repeated smell training. This is effective for patients with partial loss of smell and may help one-third of patients who have experienced chemical sensory disorders due to COVID-19.

Scientists are also researching the use of steroids to reduce inflammation as a treatment for chemical sensory recovery. When infected with COVID-19, inflammation in the body that can cause olfactory disorders rapidly increases, potentially leading to loss of smell. However, there have been disappointing experimental results. In a study conducted in France last year, 50 out of 100 COVID-19 patients received steroid nasal sprays, while the other 50 did not. Later tests on olfactory loss and recovery showed no significant difference between the two groups.

Plasma therapy is also being studied. In a 2020 study, seven patients were injected with platelet-rich plasma collected from themselves, and five showed symptom improvement. Earlier this year, the same procedure was performed on 56 patients, and research results showed slight improvement in olfactory senses, leading to preparations for large-scale trials. A research team in the UK is also studying treatments using vitamin A.