Some viruses, such as measles, mumps and meningitis, can cause hearing problems, but what about SARS-CoV-2, the virus that causes COVID-19?
In the early months of the pandemic, a rapid systematic review of COVID-19 and hearing problems revealed a possible link between COVID-19 and audio-vestibular symptoms (hearing loss, tinnitus, and vertigo). However, the quantity and quality of the early studies were low. Now that the pandemic has been going on for over a year, more studies have been published and researchers have been able to estimate the frequency of these symptoms.
My colleagues and I identified about 60 studies reporting audiovestibular problems in people with confirmed COVID-19. Our analysis of the pooled data, published in the International Journal of Audiology, shows that 7 to 15 percent of adults diagnosed with COVID-19 report audio-vestibular symptoms. The most common symptom is tinnitus (ringing in the ears), followed by hearing problems and dizziness.
Tinnitus is a common condition that affects about 17% of adults. Most people with tinnitus also have hearing loss, suggesting a close relationship between the two symptoms. In fact, tinnitus is often the first warning sign that, for example, loud noises or medications that are toxic to the ear have damaged the hearing system. Interestingly, there are reports that tinnitus is a common symptom of prolonged COVID, where symptoms persist for weeks or months after the infection has cleared.
Get free, independent, evidence-based information.
The organ of hearing is obviously extremely sensitive, as almost everyone experiences transient tinnitus when in a very quiet environment. There are also strong links between tinnitus and stress. When people stay up at night, stressed and anxious because of an upcoming appointment, financial worries or a bereavement, it is not uncommon to experience ringing in the ears.
This phenomenon usually becomes less bothersome once the source of the stress and anxiety is eliminated. Surprisingly, there are no clinical tests to diagnose tinnitus. Hearing specialists rely on self-reporting.
It is not clear why tinnitus occurs in people with confirmed COVID-19. It is possible that the virus attacks and damages the hearing system. On the other hand, the mental and emotional stress of the pandemic could be the trigger. However, these results should be interpreted with caution, as it is not always clear whether the studies report existing or new symptoms. What is missing are good quality studies comparing tinnitus in people with and without COVID-19.
Hearing loss and dizziness
Hearing problems associated with COVID-19 have been reported in a wide range of ages and severity, from mild (and treatable at home) to severe (requiring hospitalization). There are several case reports of sudden hearing loss in one ear, often accompanied by tinnitus.
Sudden hearing loss occurs in about 20 out of 100,000 people per year. It is treated with steroids to reduce swelling and inflammation of the inner ear. However, treatment is only effective if started soon after the onset of hearing loss.
We know that viruses can cause sudden hearing loss. SARS-CoV-2 could therefore be responsible for the hearing loss cases reported in COVID patients. Nevertheless, the number of COVID-19 cases worldwide is so high that it is difficult to say with certainty whether there are more cases of hearing loss than would generally be expected per year.
Another frequently reported symptom of COVID-19 is vertigo. It can be quite difficult to distinguish from the rotational vertigo that is characteristic of damage to the vestibular system in the inner ear. However, the best estimate is that rotatory vertigo occurs in about 7% of COVID-19 cases.
Beginning to understand
Given the importance of providing timely evidence to inform health services, the information from this new systematic review is welcome, but to date the evidence is based on surveys and case reports. Given the high levels of COVID-19 in the population, it is important not to diagnose audiovestibular symptoms when they do not exist or when they are incidental. However, the results of the review may only reflect the beginning of our understanding of this emerging health problem.
What is lacking are carefully conducted clinical and diagnostic studies comparing a sample of individuals who test positive for COVID-19 to a sample of non-COVID controls. To this end, we are conducting a one-year study to examine the long-term effects of COVID-19 on the audio-vestibular system in people previously hospitalized for the virus.