Long COVID Taste Loss May Not Involve Taste Buds

Taste dysfunction was gone 1 year after exposure to COVID-19, but smell loss remained for some people, a national cross-sectional study showed.

Empirically measured taste function didn't differ between individuals who had acute SARS-CoV-2 infection a year earlier and uninfected people, reported Shima Moein, MD, PhD, of Sensonics International in New Jersey and the University of Pennsylvania in Philadelphia, and co-authors.

However, olfactory dysfunction was present in 30.3% of individuals with prior COVID-19 compared with 21% of those who had no history of COVID infection (OR 1.64, 95% CI 1.18-2.27), Moein and colleagues noted in JAMA Network Open.

Long-term taste loss after COVID may reflect damage to olfactory epithelium, not taste buds, the researchers suggested. Olfactory deficits were greatest for those diagnosed with COVID when the original untyped and Alpha viral variants were prevalent.

"Our study sheds light on a critical yet often overlooked aspect of the COVID-19 pandemic: the pervasive impact of smell loss on affected individuals," Moein told MedPage Today. "Despite its prevalence, smell loss has remained largely neglected by healthcare professionals and policymakers, leading to a lack of awareness and support for affected individuals."

Self-reported survey data have suggested taste deficits persisted after SARS-CoV-2 infection but were not able to account for smell loss, Moein and co-authors noted. Other research has attempted to untangle the relationship between taste loss and olfactory dysfunction, but few have evaluated people 1 year or more after acute COVID, they added. While most people with COVID regain their sense of taste and smell within 2 years, not everyone does.

Moein and co-authors recruited people nationwide with and without a prior history of COVID from the social media website Reddit and bulletin board ads from February 2020 to August 2023. They tested taste and smell function in 340 people with prior COVID (62% women, mean age 39) and 434 people with no COVID history (64.5% women, mean age 40).

The researchers used the 53-item Waterless Empirical Taste Test (WETT) and the 40-item University of Pennsylvania Smell Identification Test (UPSIT) to assess taste and smell function. Tests were self-administered, and the COVID cohort was tested an average of 395 days after SARS-CoV-2 diagnosis.

In the COVID group, the total WETT age- and sex-adjusted mean score was 33.41 (95% CI 32.37-34.45). In the non-COVID group, it was 33.46 (95% CI 32.54-34.38; P=0.94). Subtest scores of sucrose, citric acid, sodium chloride, caffeine, and monosodium glutamate also showed no differences between groups.

UPSIT scores were lower in the COVID group compared with those who never had COVID -- a mean score of 34.3 (95% CI 33.86-34.92) versus 35.86 (95% CI 35.39-36.33; P<0.001). Neither age nor sex were specifically associated with COVID-related taste or smell scores.

A noteworthy aspect of the study was the way it recruited participants, Moein pointed out.

"Subjects were not specifically enlisted for participation in a COVID-19-related study on smell or taste," she said. "Instead, they were recruited for smell and taste testing without prior knowledge that their COVID-19 history would be utilized for grouping and analysis purposes. This approach ensured that participants experiencing smell or taste loss were not predisposed to participate differently in the study, thus enhancing the validity of our findings."

Study limitations included a lack of multiple test periods after acute infection and an inability to ascertain which SARS-CoV-2 variant participants were exposed to, the researchers acknowledged. "While PCR testing is optimal for identifying exact variants, our study faced limitations in accessing PCR data, which precluded precise variant inference," they wrote.

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