Tinnitus, commonly described as a ringing in the ears, may affect about 750 million people around the world, according to new research based on about 50 years of data.

The study, published this week in the research journal JAMA Neurology, suggests tinnitus is perceived as a major problem by more than 120 million people, most of whom are 65 or older.

Researchers estimate about 14% of adults experience tinnitus, and 2% experience a severe form of it. The prevalence also appears to increase with age: Tinnitus is reported in 10% of adults ages 18 to 44, 14% of adults ages 45 to 64, and 24% of those 65 and older.

The findings align with earlier estimates. The American Tinnitus Association estimates nearly 15% of people, or more than 50 million Americans, experience tinnitus. The National Institute on Deafness and Other Communication Disorders says about 10% of U.S. adults, or nearly 25 million people, have experienced tinnitus lasting at least five minutes in the past year.

“This study suggests that the global burden of tinnitus is large, similar to migraine and pain, and the lack of effective treatment options justifies a major investment in research in this area,” researchers wrote.

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What is tinnitus?

While tinnitus is commonly known as a ringing sound in the ears, it can take many other forms, including buzzing, hissing, whistling, swooshing and clicking noises, according to the American Tinnitus Association (ATA). In rare cases, it can sound like music.

The sounds can be soft or loud, high- or low-pitched, and can occur in either one or both ears, according to the National Institute on Deafness and Other Communication Disorders (NIDCD).

The condition can either be temporary or chronic, the ATA said. It’s not a disease in itself but is a symptom of other underlying health conditions, according to the association.

What causes tinnitus?

In most cases, tinnitus is a reaction in the brain to damage in the ear or auditory system, according to the ATA. However, the association says, tinnitus can also be a symptom of roughly 200 health problems, including hearing loss, obstructions in the middle ear, and head and neck trauma.