dcyphr | Incomplete and late recovery of sudden olfactory dysfunction in COVID-19


Olfactory dysfunction (issues with one’s sense of smell) is a symptom which has recently been associated with COVID-19. With this being said, there is little data on the duration of the condition or on patient recovery timelines. This paper used a series of online surveys to analyze the symptom’s relationship with COVID-19 and to gain recovery data. 



Anosmia (loss of sense of smell) has been added to the extensive list of symptoms associated with COVID-19, alongside respiratory issues. One study showed that only 5.1% of coronavirus patients in Wuhan experienced anosmia, but over 85% of coronavirus patients in Europe experienced changes in their smelling (hyposmia or anosmia). This second statistic is inconsistent with smelling problems tied to other viruses. This discrepancy led the Brazilian Academy of Rhinology and the Brazilian Association of Otorhinolaryngology and the Cervical-Facial Surgery to conduct the following investigation. 


The organizations listed above put together an online survey which was sent out to physicians treating COVID-19 patients experiencing problems related to smell. The survey collected epidemiological information (related to the occurrence and spread) of patient anosmia and hyposmia along with associated symptoms, comorbidities, treatments used, recovery, and COVID-19 test results. The study ran between March 25 and April 30, 2020 and utilized various social media platforms. Prevalence statistics were communicated as a percent, while factors such as symptom duration and patient age were shared using medians. Further statistical methods, such as the Mann-Whitney U test, were also used.


A total of 253 patients from all over Brazil were part of this study (geographic distributions are provided in the paper). 149 were women and 104 were men, with an average age of 36. 212 of the patients reported sudden anosmia and 196 reported accompanying “nonspecific inflammatory symptoms” such as cough, fever, headache, myalgia, fatigue, etc. 111 patients reported nasal symptoms such as obstruction, sneezing, nasal burning, etc. Only 36% of patients reported comorbidities, the most common being mucus membrane swelling or inflammation, asthma, and systemic arterial hypertension.   

Treatment included (in order of prevalence) nasal saline irrigation, analgesics (pain relievers), topical intranasal corticosteroids, antibiotics, oral corticosteroid, hydroxychloroquine, oseltamivir, and olfactory training. 

Recovery information was gathered from medical records of 227 of the study participants. 121 individuals reported full recovery, 76 partial recovery, and 30 no recovery. The average time required for a full recovery was 12.5 days. Follow up time had a median of 21 days. 183 of the participants were tested for COVID-19, with 145 coming back as positive and 28 negative. Patients who weren’t tested were younger, didn’t experience as many nonspecific inflammatory symptoms, and had shorter follow up times. 

Further analysis was performed to compare patients who tested positive for coronavirus and those who tested negative. No epidemiological differences were noted between the two groups. Nonspecific inflammatory symptoms (listed above) appeared in COVID positive patients more frequently. Other symptoms did not show any statistical connection to one group in particular. Patients with confirmed COVID-19 tended to have a lower full recovery rate and a longer duration of olfactory dysfunction. Positive patients with hyposmia (reduced sense of smell) were more likely to fully recover compared to those with anosmia (full loss of smell). The treatments listed showed no connection to likelihood of recovery. 


A major finding of this study is that COVID-19 is associated with prolonged olfactory dysfunction and with reduced rates of recovery from it. Only half of COVID positive patients fully recovered, compared to over 70% of COVID negative patients. COVID positive individuals who experienced recovery took an average of 5 days longer to achieve it. 

Females have experienced olfaction loss in numbers greater than men during the COVID-19 pandemic. They make up 75% of reported cases (⅔ with confirmation of coronavirus). This statistic is very interesting, as studies show that olfactory dysfunction is generally more prevalent in men. This discrepancy may be due to male inability to recognize their reduced sense of smell, or women paying more attention to their health. Another interesting finding is that anosmia is more prevalent than hyposmia in COVID-19 patients (opposite of findings for the general population).  

Sudden loss of sense of smell is generally not common, with only 16% of patients showing no other symptoms. Only 5.5% of the COVID-19 patients had “isolated sudden olfactory dysfunction.” With this being said, sudden anosmia may be connected to milder cases of COVID-19. It is important to note that changes in taste were not included in this study. 

Limitations in the number of participants tested for COVID-19 and in the limited follow up window are all acknowledged by the researchers.