Good news for people struggling with sensory problems after a bout of COVID-19. Although mild cases of the disease often impair the ability to taste and smell, and the problem can drag on for months, a new study from Italy shows that most people return to their senses, as it were, within 3 years.
said Paolo Boscolo-Rizzo, MD, a professor of medicine, surgery, and health sciences at the University of Trieste (Italy), and a co-author of the study, published as a research letter in JAMA Otolaryngology–Head & Neck Surgery.
Dr. Boscolo-Rizzo and his colleagues analyzed data from 88 adults with mild COVID-19, which was defined as having no lower respiratory disease and blood oxygen saturation of 94% or greater. Another group of 88 adults who never contracted the virus but sometimes had difficulties with smell and taste were also studied. In both groups, the average age was 49 years, all participants were White, and 58% were women.
The researchers tested participants’ sense of smell with sticks that contained different odors and checked their sense of taste with strips that had different tastes. Over time, fewer people had difficulty distinguishing odors. Three years after developing COVID-19, only 12 people had impaired smell, compared with 36 people at year 1 and 24 people at year 2. And at the 3-year mark, all participants had at least a partial ability to smell.
The story was similar with sense of taste, with 10 of 88 people reporting impairments 3 years later. By then, people with COVID-19 were no more likely to have trouble with smell or taste than people who did not get the virus.
A study this past June showed a strong correlation between severity of COVID-19 symptoms and impaired sense of taste and smell and estimated that millions of Americans maintained altered senses. More than 10% of people in the Italian study still had trouble with smell or taste 3 years later.
Emerging treatments, psychological concerns
“We’re seeing fewer people with this problem, but there are still people suffering from it,” said Fernando Carnavali, MD, an internal medicine physician and a site director for the Center for Post-COVID Care at the Icahn School of Medicine at Mount Sinai, New York City.
Dr. Carnavali wasn’t part of this study, but he did find the new results encouraging, and he called for similar studies in diverse populations that have experienced COVID-19. He also noted that an impaired sense of smell is distressing.
“It really has a significant psychological impact,” Dr. Carnavali said.
He recalled a patient crying in his office because her inability to smell made it impossible for her to cook. Dr. Carnavali recommended clinicians refer patients facing protracted loss of smell or taste to mental health professionals for support.
Treatments are emerging for COVID-19 smell loss. One approach is to inject platelet-rich plasma into a patient’s nasal cavities to help neurons related to smell repair themselves.
A randomized trial showed platelet-rich plasma significantly outperformed placebo in patients with smell loss up to a year after getting COVID-19.
“I wish more people would do it,” said Zara Patel, MD, an otolaryngologist at Stanford (Calif.) Medicine, who helped conduct that trial. She said some physicians may be nervous about injecting plasma so close to the skull and are therefore hesitant to try this approach.
Another technique may help to address the olfactory condition known as parosmia, in which patients generally experience a benign odor as rancid, according to otolaryngologist Nyssa Farrell, MD, of Washington University School of Medicine, St. Louis. Dr. Farrell said around two-thirds of patients who contract COVID-19 develop the condition, and the rates of long-term parosmia range from 10%-50% depending on various studies.
“It is almost always foul; this can profoundly affect someone’s quality of life,” impairing their ability to eat or to be intimate with a partner who now smells unpleasant, said Dr. Farrell, who wasn’t associated with this research.
The treatment, called a stellate ganglion block, is provided through a shot into nerves in the neck. People with parosmia associated with COVID-19 often report that this method cures them. Dr. Patel said that may be because their psychological health is improving, not their sense of smell, because the area of the body where the stellate ganglion block is applied is not part of the olfactory system.
Earlier this year, Dr. Farrell and colleagues reported that parosmia linked to COVID-19 is associated with an increased risk for depression, anxiety, and suicidal ideation.
One coauthor reported receiving grants from Smell and Taste Lab, Takasago, Baia Foods, and Frequency Therapeutics. The other authors reported no relevant financial relationships.
A version of this article first appeared on Medscape.com.