Some COVID-19 cases were found to have had an impaired sense of smell—but not taste—for at least one year, according to a new study published in JAMA.
The U.S.-based study compared 340 individuals with and 434 without a prior COVID-19 infection, said researchers. They were recruited between February 2020 and August 2023, it added.
Participants in the study were asked to take the Waterless Empirical Taste Test and the University of Pennsylvania Smell Identification Test to determine their smell and taste.
Participants who had COVID-19 were more likely—or 30.3 percent—to have some amount of smell loss as compared with individuals who did not have a history—at 21 percent—it found. A moderate-to-severe loss of smell was higher in people with prior COVID-19 cases, with 8.5 percent of prior COVID-19 cases saying they had a loss of smell as compared with 2.8 percent who said they did not have COVID-19.
The researchers also noted that “taste function did not differ between individuals who had contracted COVID-19 one year earlier and those who had not, whereas some olfactory (smell) dysfunction was present in 30.3 percent of individuals with prior COVID-19,” according to the paper. “But only 21.0 percent of individuals with no history of infection. Deficits were greatest for individuals with the original untyped and Alpha variant infections.”
“Self-report surveys suggest that long-lasting taste deficits may occur after SARS-CoV-2 infection, influencing nutrition, safety, and quality of life,” it said. “However, self-reports of taste dysfunction are inaccurate, commonly reflecting deficits due to olfactory not taste system pathology; hence, quantitative testing is needed to verify the association of post-COVID-19 condition with taste function.”
Meanwhile, “reports that taste loss continues long after the initial infection probably are due in large part to the confusion between taste- and olfaction-dependent food flavor,” the study’s authors explained. “Smell loss remained in nearly one-third of individuals with exposure, likely explaining taste complaints of many individuals with [long COVID].”
Over the course of the pandemic, many people who have tested positive have reported a loss of taste or smell. And a number of health agencies worldwide have identified both as a major symptom of the virus, which first emerged in late 2019 in Wuhan, China.
The research had “revealed widespread infiltration of T-cells engaged in an inflammatory response in the olfactory epithelium, the tissue in the nose where smell nerve cells are located,” a Duke news release states. “This unique inflammation process persisted despite the absence of detectable SARS-CoV-2 levels.”
