Among the common symptoms of long COVID are dizziness, tinnitus, and ear pain, according to the National Institute for Health and Care Excellence in the United Kingdom.

Other viral infections — including rubella, measles, and cytomegalovirus — are known to cause hearing problems, but research into possible links between COVID-19 and hearing issues remains at an early stage.

In June 2020, specialists at the Manchester Centre for Audiology and Deafness (ManCAD) in the U.K. reviewed seven studies that hinted at a link between hearing and balance, or audiovestibular, problems and COVID-19.

At that time, however, the quality of the evidence supporting a possible association was poor.

The same researchers have now updated their review to include 56 studies published in 2020.

Although the evidence remains tentative, the researchers have estimated the prevalence of audiovestibular problems among people who have recovered from a SARS-CoV-2 infection.

Their analysis suggests that around 14.8% of patients experience tinnitus, or “ringing in the ears,” 7.6% have hearing loss, and 7.2% have rotatory vertigo, which is a sensation of spinning.

The review appears in the International Journal of Audiology.

Possible overestimates

The authors emphasize that these figures may overestimate the true scale of the problem.

This is because the reports that they reviewed do not always make it clear whether the symptoms were new or whether they were preexisting symptoms that had temporarily become worse.

In addition, most of the studies were based on medical records or questionnaires in which patients reported their own symptoms, rather than the appropriate hearing tests.

“There is an urgent need for a carefully conducted clinical and diagnostic study to understand the long-term effects of COVID-19 on the auditory system,” says senior author Kevin Munro, professor of audiology at ManCAD.

“Though this review provides further evidence for an association, the studies we looked at were of varying quality, so more work needs to be done,” he adds.

Prof. Munro is leading a year-long study in the U.K. that will compare control patients with patients who recovered after being hospitalized with COVID-19.

He and his colleagues hope to get a more accurate picture of the incidence and severity of COVID-related hearing issues, as well as which parts of the auditory system are affected.

They will also investigate possible associations between audiovestibular problems and other factors, such as lifestyle, other medical conditions, and the treatments the patients received in intensive care.

Prof. Munro explains:

“Over the last few months, I have received numerous emails from people who reported a change in their hearing, or tinnitus after having COVID-19. While this is alarming, caution is required, as it is unclear if changes to hearing are directly attributed to COVID-19 or to other factors, such as treatments to deliver urgent care.”