Around one in 20 people who have tested positive for COVID-19 worldwide have long-term smell or taste problems for at least 6 months, a new study has found.
The survey was put together by a team of international experts, including some from the UK and analysed data from 18 studies comprising 3,699 patients.
Published in the BMJ, it used modelling to estimate how many people go on to suffer from altered taste or smell for at least six months after a COVID-19 infection. It found that an estimated 5.6% of patients suffer smell dysfunction for at least six months, while 4.4% have a change in taste.
15 million people may suffer from loss of smell
By this month there had been around 550 million COVID infections globally, meaning 15 million may have had smell problems and 12 million had taste issues, the study estimated.
It added that women are less likely to recover their sense of smell and taste and patients who suffered the most at the initial infection were more likely to have long-term issues.
In a linked editorial, a team of Italian academics wrote: "Health systems should therefore be ready to provide support to these patients who often report feeling isolated when their symptoms are overlooked by clinicians."
They added that people "only realise the importance of smell when it is lost" and they can be "severely distressed" when they lose these senses.
"Loss of smell and taste adversely affects quality of life by depriving those affected of several everyday pleasures and social bonds," the team, led by Paolo Boscolo-Rizzo from the University of Trieste, wrote.
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"People can also experience anorexia, food aversions, malnutrition, anxiety, and depression," they added.
They highlighted that parosmia - the experience of a distorted sense of smell - means that for many this "transforms a pleasant odour into an unpleasant one".
This means that "daily activities such as smelling coffee and sensing the flavour of food can become disgusting and emotionally distressing".