Long COVID tied to loss of smell that may be permanent


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Center for Infectious Disease Research and Policy

Mary Van Beusekom | News Writer | CIDRAP News

An observational study of 219 unvaccinated long-COVID patients with neurologic symptoms in the Amazon concludes that 64% had a persistently impaired sense of smell, which the authors said could be permanent.

Brazilian researchers evaluated 219 adult long-COVID patients at a rehabilitation center at a public university in the Amazon from Sep 9, 2020, to Oct 20, 2021. A total of 74.9% of the patients were women, 88.6% were 18 to 59 years old, 94.1% had more than 9 years of education, and 52.5% had a monthly income of up to US $192.

Most had likely been infected with wild-type SARS-CoV-2 because symptom onset occurred in spring 2020. Participants underwent neurologic examination and completed a questionnaire about their daily activities.

Hazard detection, food intake affected

Of the 219 patients, 139 (63.5%) were diagnosed as having some degree of chronic olfactory dysfunction (anosmia [loss of smell] or hyposmia [decreased sense of smell]), per the Connecticut Chemosensory Clinical Research Center test.

Patients with an impaired sense of smell had long-COVID symptoms for significantly longer than those with normal olfaction (average days, 242.7 vs 221.0), and a higher proportion had neurologic symptoms for more than 6 months (79.1% vs 63.8%).

There was a significant link between anosmia and interference with daily activities, namely impaired hazard detection, personal hygiene, and food intake (all 67.7%). More participants with a normal sense of smell than those with impaired olfaction reported headache (53.8% vs 37.4%), sleep disorders (36.3% vs 23.0%), and anxiety (45.0% vs 21.6%), while a greater proportion of the anosmia group also lost their ability to taste (ageusia, 59.7% vs 23.8%).

Hospitalization rates didn’t differ significantly between participants with normal or impaired olfaction (20.0% vs 13.7%).

Condition may last more than 1 year

The study authors noted that most COVID-related olfactory disorders last only 2 or 3 weeks. But chronic olfactory disorders, they said, have been linked to disturbed eating patterns, depression, and reduced quality of life and can lead to difficulties with cooking, health and nutrition maintenance, personal hygiene, and social relationships.

These patients are three times more likely to be endangered by smoke inhalation, delayed detection of gas leaks, and spoiled food, the authors said.

They called a reduced ability to smell “one of the most important long-term neurologic symptoms of COVID-19, with the highest prevalence seen among women, adults, and outpatients. Patients with olfactory dysfunction may experience persistent severe hyposmia or anosmia more than 1 year from the onset of symptoms, suggesting the possibility of the condition becoming a permanent sequela.”

The findings underscore the need for continued monitoring of the rate of recovery of olfactory function in long-COVID patients, the researchers said. “In addition, clinical trials and longitudinal studies are recommended to verify the effectiveness of potential treatments and the postulated risk for an increase in neurologic sequelae or neurodegenerative disorders in this population,” they wrote.