Many people who recovered from Covid-19 are continuing to live with a hidden health issue — a weakened sense of smell that can last for years. A large study has shown that even when individuals believe their ability to smell has returned to normal, many still perform poorly on scientific smell tests long after infection.
Researchers from the US National Institutes of Health and New York University Langone Health carried out an investigation involving 3,535 men and women. Each participant underwent a clinical evaluation using a 40-odour test designed to measure the accuracy of scent detection. The results have been published in the journal JAMA Network Open.
According to the study, four out of five participants who had earlier noticed changes in their sense of smell after contracting Covid scored poorly on the evaluation when tested nearly two years later. Within this group, close to one-fourth were found to be either severely impaired or had completely lost their sense of smell.
The researchers also discovered that the condition is not always noticed by those affected. Among participants who had been infected with Covid but did not report any change in their smelling ability, two-thirds still recorded abnormally low scores in the clinical test.
The findings further showed that smell-related issues were not limited only to those who had tested positive for the virus. Even among participants who were never infected and had not reported any olfactory problems, more than half performed poorly in the evaluation.
Scientists say the results underline the importance of recognising smell loss as a possible long-term impact of Covid-19. They suggest that health systems consider including smell testing in routine post-Covid care. Work is also under way to find methods that can help patients regain their sense of smell, including treatments with vitamin A and specialised training exercises aimed at retraining the brain to respond to odours.
