SYDNEY, AUSTRALIA - AUGUST 22: Tap dancers dressed in nose shaped costumes perform during the ... [+]
A study of 340 people with a prior Covid-19 infection reported that some degree of smell loss persisted in close to one-third of the participants one year post-exposure, although a loss of taste was absent.
"The major finding of this cross-sectional study was that taste function was not meaningfully altered 1 year after having Covid-19. In contrast, some degree of olfactory dysfunction remained in nearly one-third of individuals with post-Covid condition (also known as long Covid),” the researchers wrote in their study that was published in JAMA Network Open on April 23, 2024. “Reports that taste loss continues long after the initial infection probably are due in large part to the confusion between taste- and olfaction (ability to smell)-dependent food flavor. The latter is due to molecules reaching the olfactory receptors from the oral cavity via the nasopharynx. Taste buds mediate only sweet, sour, bitter, salty, and umami oral sensations.”
“Our finding that more recent SARS-CoV-2 variants, most notably Omicron, exhibited less frequent smell loss accords with findings from earlier studies,” they added.
A 2023 Rhinology study found that the prevalence of smell loss among people who were infected with the Omicron variant (36.3%) was significantly lower than that of people infected with the original Covid-19 variant (80.6%), Alpha variant (83%), and Delta variant (65.6%).
In the United States alone, researchers estimate that anywhere between 10 million to 35 million adults of working age live with post-Covid condition or long Covid. “Although post-Covid condition encompasses a diverse array of new, recurring, or persistent health problems, effective health policy requires a precise understanding of the prevalence of individual symptoms and their impact on daily life and work. Such understanding is a prerequisite for providing survivors of COVID-19 with the types of support they may need,” the researchers explained.
To examine and evaluate the long-term outcomes associated with Covid-19, the researchers recruited participants based in the United States via advertisements posted on Reddit and local bulletin boards from February 2020 to August 2023. They enrolled 434 healthy participants with no history of a Covid-19 infection and 340 patients who had a prior infection.
Each participant underwent tests that determined whether they could effectively taste flavors with the help of plastic taste strips. Their ability to identify different odorants was tested using microcapsules embedded with 10 sniff odorants that the researchers had placed on brown strips at the bottom of each page.
The researchers observed that the participants with a history of Covid-19 were more likely to experience some degree of smell loss compared with those without such a history — 103 individuals (30.3%) vs 91 individuals (21%). The incidence of partial or full loss of smell was also higher in the group with a history of Covid-19 (8.5%) compared with the group without Covid-19 history (2.8%).
"Test scores of participants with the original and Alpha variant infections were the only ones to differ significantly from test scores of participants with no history of COVID-19," the researchers noted. "For example, total to severe loss occurred in 10 of 42 individuals with the Alpha variant infection (23.8%) and 7 of 52 individuals with the original variant infection (13.5%) compared with 12 of 434 individuals (2.8%) with no COVID-19 history."
