Since the pandemic was declared in early 2020, COVID-19-related anosmia quickly emerged as a telltale sign of infection. However, the time course and reversibility of COVID-19-related olfactory disorders, which may persist and negatively affect patients, require further study.
To clarify the clinical course and prognosis, we followed a cohort of patients with COVID-19-related anosmia for 1 year and performed repeated assessments of olfactory function for a subset of patients.
Methods
This cohort study follows the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. Participants provided written informed consent. The study was approved by the ethics committee of the University Hospitals of Strasbourg.
In April 2020, we published a study on a cohort of patients with polymerase chain reaction-proven COVID-19 with acute loss of smell (lasting more than 7 days). Over the course of 1 year, at 4-month intervals, patients were asked to complete a survey and their olfactory function was assessed using psychophysical tests (threshold and identification tests; Sniffin’ Sticks Test; Burghardt).
Hyposmic or anosmic patients were followed until objective olfactory recovery (normal results were defined as those at or above the 10th percentile). Data analysis was conducted from June 2020 to March 2021.
Results
We evaluated 97 patients (67 women [69.1%]; mean [SD] age, 38.8 [11.5] years) with acute loss of smell beyond 7 days. Of these patients, 51 (52.6%) underwent both subjective and objective olfactory testing, and 46 (47.4%) underwent subjective evaluation alone.
After subjective evaluation at 4 months, 23 of 51 patients (45.1%) reported complete recovery of smell, 27 of 51 patients (52.9%) reported partial recovery, and 1 of 51 patients (2.0 %) did not report recovery.
On psychophysical testing, 43 of 51 patients (84.3%) were objectively normosmic, including 19 of 27 (70.0%) who self-assessed as only partially recovered (all patients who self-reported a normal return of smell were corroborated with objective tests.
The remaining 8 patients (15.7%) with persistent subjective or objective loss of smell were followed up at 8 months, and another 6 patients became normosmic on objective testing.
At 8 months, objective olfactory evaluation confirmed complete recovery in 49 of 51 patients (96.1%).
Two patients remained hyposmic at one year, with persistent alterations (1 with abnormal olfactory threshold and 1 with parosmia causing abnormal identification).
Among those who underwent subjective evaluation only, 13 of 46 patients (28.2%) reported satisfactory recovery at 4 months (7 with complete recovery and 6 with partial recovery), and the remaining 33 patients (71.7% ) they did it after 12 months (32 with total recovery). total and 14 with partial recovery).
Discussion
More than 1 year into the pandemic, we describe the long-term prognosis for a cohort of patients with COVID-19-related anosmia, the majority of whom (96.1%) objectively recovered by 12 months.
Our findings suggest that an additional 10% increase in recovery can be expected at 12 months, compared to studies with 6 months of follow-up that found only 85.9% of patients with recovery. This supports findings from pivotal animal research, involving both imaging studies and post-mortem pathology , suggesting that COVID-19-related anosmia is likely due to peripheral inflammation.
We also confirmed that there are discrepancies between self-assessed and objective tests, so participants tend to underestimate the return of normosmia. This highlights the importance of applying both methods for the evaluation of postviral olfactory disorder.
Discrepancies could be explained by qualitative disorders that disrupt self-assessment (e.g., Parosmia) and/or limited ability of olfactory tests to capture a full return to function among individuals with higher baseline olfactory abilities.
The main limitation of our study was that only half of the cohort underwent objective olfactory testing. However, all participants were contacted at 12 months and almost all reported a subjective return of smell.
It is also worth noting that our cohort consisted mainly of women and younger patients (<50 years), both factors positively associated with complete olfactory recovery6.
Conclusions Persistent anosmia related to COVID-19 has an excellent prognosis with almost complete recovery at one year. As doctors treat an increasing number of people with post-COVID syndrome, data on long-term outcomes are needed for informed prognosis and advice. |
Commentary in plain language
A year later, almost all patients in a French study who lost their sense of smell after a COVID-19 attack regained that ability, researchers report.
" Persistent anosmia related to COVID-19 has an excellent prognosis, with almost complete recovery at one year," according to a team led by Dr. Marion Renaud, an otolaryngologist at Strasbourg University Hospitals.
At the beginning of the pandemic, doctors treating people infected with SARS-CoV-2 began to realize that a sudden loss of smell was a characteristic of the disease. The culprit in these cases is thought to be COVID-linked "peripheral inflammation" of the nerves that are crucial to olfactory function.
But as months passed and many patients did not regain their sense of smell, some began to worry that the damage could be permanent.
The new study should ease those fears.
In their research, the French team tracked the sense of smell of 97 patients (67 women, 30 men) with an average age of around 39 years. They had all lost their sense of smell after contracting COVID-19.
Patients were asked about any improvements in their ability to smell at four months, eight months, and then a full year after the loss of smell began. About half also received specialized tests to measure their ability to smell.
At the four-month mark, objective testing of 51 of the patients showed that approximately 84% (43) had already regained their sense of smell, while six of the remaining eight patients had done so by the four-month mark. eight months. Only two of the 51 patients who had been analyzed using the specialized tests had any impaired sense of smell a year after their initial diagnosis, the findings showed.
Overall, 96% of patients objectively recovered by 12 months, Renaud’s team reported. The study was published online June 24 in JAMA Network Open .
Dr. Theodore Strange is interim chair of medicine at Staten Island University Hospital in New York City. He was not involved in the new study, but called the findings "very encouraging."
"The good news is that loss of smell is not a permanent sequelae of COVID disease," Strange said.
That sentiment was shared by Dr. Eric Cioe-Peña, director of global health at Northwell Health in New Hyde Park, N.Y. He said the findings, while very welcome, should remind everyone, especially young people, that a SARS infection -CoV-2 can cause a lot of damage in the long term.
"It is important that as the public examines the vaccine, some to determine whether the ’risk is worth the benefit,’ that we take into account not only hospitalization and death, but also these ’long-lasting’ symptoms, which can affect people for months and years after recovering from the virus itself," Cioe-Peña noted.
"The most important thing to take away from this study," he said, "is to get vaccinated in the first place and prevent exposure to prolonged symptoms."
