In a small study of 100 people who contracted COVID-19 in the first wave, more than half have long-term changes to their sense of smell, according to preliminary research published Jan. 20 by MedRxiv.
In the early days of the pandemic, temporary loss of smell emerged as a common indicator of COVID-19. However, not much is known about long-lasting effects on olfactory dysfunction. To establish prevalence 18 months after infection, researchers at the Karolinska Institute in Sweden ran tests on 100 healthcare workers who had COVID-19 in the first wave of spring 2020. Since it was early in the pandemic, none of the volunteers were vaccinated at the time of infection.
Scientists ran the same tests on a control group of people who tested negative for COVID-19 antibodies. About a fifth had deficiencies in sense of smell, implying that smell disorders were common in the general population before the pandemic.
The study has yet to be peer reviewed.
Three things to know:
1. Overall, 65 percent of participants who had COVID-19 displayed either a loss of smell, a reduced sense of smell, or distortions to the sense 18 months after infection, compared to 20 percent of those who had not had COVID-19. "Given the amount of time since [the] initial insult to the olfactory system, it is likely that these olfactory problems are permanent," the authors wrote.
2. A third of participants had a reduced ability to detect odors, and nearly half had parosmia, where sense of smell is distorted.
3. After 18 months, only 3 percent had lost sense of smell entirely.
Early U.K. study findings suggest that a loss of smell or taste is much less common with omicron than the delta variant, but Johan Lundström, PhD, an author of the Karolinska Institute study, told The Guardian that there isn't reliable data demonstrating that omicron is any less dangerous to the olfactory system.