A loss of smell from Covid-19 could be down to a genetic risk factor, a new study suggests.
While the precise cause of sensory loss from Covid-19 remains unclear, scientists believe the virus damages cells in a part of the nose called the olfactory epithelium.
Cells in this part of the nose protect olfactory neurons, which help humans smell.
Using data from genetics testing company 23andMe, researchers in the US compared the genetic differences between people who tested positive for Covid-19 and lost their sense of taste or smell, and those who did not.
They identified a locus – the specific position of a gene on a chromosome – near two genes, UGT2A1 and UGT2A2.
The UGT2A1 and UGT2A2 genes are expressed within the olfactory epithelium. They play a role in the way we metabolise smells.
People with this genetic locus are more likely to experience a loss of smell, experts said.
It is unclear how UGT2A1 and UGT2A2 are involved in the process, but these “genes may play a role in the physiology of infected cells and the resulting functional impairment that contributes to loss of ability to smell”, the study said.
“It was this really beautiful example of science where, starting with a large body of activated research participants who have done this 23andMe test, we were able to very quickly gain some biological insights into this disease that would otherwise be very, very difficult to do,” Adam Auton, vice president of human genetics at 23andMe and the lead author of the study told Sky News.
The UK first recognised a loss of smell or taste as symptoms of Covid-19 in May 2020.
All 69,841 people who took part in the study had Covid-19 and 68 per cent reported a loss of smell or taste.
Women were more likely to report the symptom than men, with 72 per cent experiencing a loss of taste or smell compared to 61 per cent of men.
Additionally, scientists found that people from East Asian or African American descent are less likely to report a loss of smell or taste.
