Study Results Show Olfactory Dysfunction Due to COVID-19 May Last for More Than a Year

Highest prevalence is seen among adults, outpatients, and women and can cause persistent severe anosmia or hyposmia, findings indicate.

Olfactory dysfunction, a long-term neurologic symptom of COVID-19 with the highest prevalence seen among adults, outpatients, and women can cause persistent severe anosmia or hyposmia more than 1 year from the onset of symptoms, suggesting the possibility of it becoming permanent, new study results show.

In the cross-sectional study published in JAMA Network Open, investigators included 219 individuals with long COVID and self-reported neurological symptoms from a rehabilitation center at a public university in the Amazon region of Brazil.

The study took place between September 9, 2020, and October 20, 2021, and 139 individuals received a diagnosis of chronic olfactory dysfunction, confirmed by the Connecticut Chemosensory Clinical Research Center test. The other 80 individuals had normosmia.

Investigators prepared and collected electronic case report forms for the individuals’ clinical and sociodemographic data. The association between daily life and olfactory dysfunction were recorded with a questionnaire.

Investigators found that individuals with olfactory dysfunction had a significantly longer duration of long COVID symptoms than those with normosmia at 101.9 days and 97.5 days, respectively.

Further, individuals with olfactory dysfunction had a higher proportion of neurologic symptoms for more than 6 months than the normosmia group.

Additionally, among those with anosmia, there was a significant association between daily activities and olfactory dysfunction, including impairment in food intake, hazard detection, and personal hygiene, all at 67.7%.

Furthermore, ageusia symptoms were associated with the occurrence of olfactory dysfunction at 11.14, whereas headaches were present at 0.41 and sleep disorders at 0.48 showed an inverse association with olfactory dysfunction.

Inverse associations for headaches at 0.35, sleep disorders at 0.48, and no hospitalizations at 2.14 were associated with severe olfactory dysfunction.

The results also showed that those with chronic olfactory dysfunction had a high risk of developing mood disorders, such as anxiety and depression, and neurodegenerative diseases, such as Alzheimer and Parkinson disease.

Investigators said that previous studies also found similar results, with olfactory dysfunction linked to being female, middle aged, an outpatient, and lower probability of being admitted to the hospital because of COVID-19.

A limitation of the study is that dysgeusia was not evaluated with a psychological test, so there could have been an overestimation of the symptom in the sample, and it was not known whether the reported difficulties in food intake were because of the severity of the dysgeusia, olfactory dysfunction, or both, investigators said.

Additionally, because of long COVID being categorized by multiple symptoms, the quality-of-life association might have been because of the interactions of symptoms, not just olfactory dysfunction.

Furthermore, the qualitative olfactory disorders, including cacosmia, parosmia, and phantosmia were not analyzed. However, this information is being collected as part of the follow-up research of this cohort and will be published in the future.

Reference

Mendes Paranhos AC, Nazareth Dias ÁR, Machado da Silva LC, et al. Sociodemographic characteristics and comorbidities of patients with long COVID and persistent olfactory dysfunction. JAMA Netw Open. 2022;5(9):e2230637. doi:10.1001/jamanetworkopen.2022.30637