Prednisolone fails to improve olfactory function following COVID-19

Prednisolone does not improve olfactory function following COVID-19, is the conclusion drawn from a new study published in BMC Medicine. Therefore, the authors do not recommend prescribing prednisolone for patients with persistent olfactory disorders after COVID-19. 

"Prednisolone does not improve the sense of smell after COVID-19," the authors wrote in the study executed by UMC Utrecht. Also, in most patients- regardless of prednisolone use-sense of smell gradually improved over time. 

During the corona pandemic, more and more people noticed that they could not smell or taste after having been infected with the SARS-CoV-2 virus. As the persistent loss of smell is thought to be caused by an inflammatory response, corticosteroids might be a treatment option. Therefore, researchers from several universities and hospitals started last year a large randomized, double-blind study to investigate the possible role of prednisolone to improve the loss of smell and taste due to COVID-19. This drug has been suggested as a treatment for olfactory disorders after COVID-19, but evidence of its efficacy is scarce. 

No improvement with prednisolone

"The results of our study in 115 patients show that after 3 months of treatment there is no greater improvement in the sense of smell in patients who were on prednisolone (40 mg/day for 10 days, starting at least 4 weeks after infection) as compared to those who received a placebo", says ear-nose-throat surgeon Digna Kamalski from UMC Utrecht, who coordinated the study. "We did see that the sense of smell of both groups of patients continued to improve, even long after the corona infection has occurred. That, of course, is good news."

Smell function recovers by itself

In the ZonMW-funded research project "Sniffing out COVID," several studies are underway, including the course of loss of smell and taste as a result of COVID-19 and whether smell and taste recover on their own and to what extent. Now that the results of this study are known, there will be a follow-up. Digna: "We have invited all patients to be tested again after 1 year, as we are very interested to know whether or not the improvement persists."

Olfactory disorders after COVID-19

Olfactory disorders (dysfunction of smell) are a common early feature in COVID-19, occurring in about two of every three patients. Although most patients recover within 4 weeks, it is reported that up to 46 percent of patients still have impaired smell after 6 months and 20–60 percent after a year. The prevalence of long-term olfactory disorders varies widely because of the different methods of assessing olfactory function and a lack of follow-up. Patients with persistent olfactory disorders are at increased risk of having depressive symptoms and nutritional issues, both decreasing quality of life.

Reference:

Schepens, E.J.A., Blijleven, E.E., Boek, W.M. et al. Prednisolone does not improve olfactory function after COVID-19: a randomized, double-blind, placebo-controlled trial. BMC Med 20, 445 (2022). https://doi.org/10.1186/s12916-022-02625-5