An ashtray containing a cigarette.

Smoking cigarettes may raise the risk of hearing loss—and the more you smoke, the higher your risk, reveals a study of more than 50,000 adults in Japan published today in the journal Nicotine & Tobacco Research.

"These results provide strong evidence to support that smoking is a causal factor for hearing loss and emphasize the need for tobacco control to prevent or delay the development of hearing loss," Huanhuan Hu, Ph.D., senior researcher with Japan's National Center for Global Health and Medicine and the study's lead author, said in a statement.

Results of previous studies on a possible connection between smoking and hearing loss have been been mixed. The Tokyo researchers pointed out that earlier studies have generally had fewer test subjects or relied on self-reported hearing loss, rather than on the results of actual hearing tests. 

Here's what this new study means and how to protect your hearing.

What the New Study Means

The research team followed 50,195 adults with no hearing loss for up to eight years in the new study.

Workers in Japan are required to have a yearly health exam, including a hearing test, which helped the researchers determine how many people developed hearing loss over the course of the study.

More on Hearing Loss

Among those who’d never smoked, about eight in 1,000 people developed high-frequency hearing loss every year. That's the kind that can make it difficult to understand speech.

The rate was nearly twice as high in smokers: 15 people out of every 1,000 developed that type of hearing loss.

And the more cigarettes a person smoked on a daily basis, the more likely he or she was to experience hearing loss.

That particular finding is pretty convincing, says Marvin M. Lipman, M.D., Consumer Reports’ chief medical adviser, but several limitations make the study less than definitive.

For instance, researchers had no information on workplace noise exposure for many of the study subjects, so they couldn't account fully for its possible effects on hearing.

Also, almost all of the participants were men, so these findings may not apply to women, says Sharon Curhan, M.D., Sc.M., a physician and epidemiologist at Brigham and Women's Hospital and Harvard Medical School, who was not involved in the study.

What's more, she has concerns about the type of hearing test used (a simple pass/fail test at a single frequency) which she said is “not the optimal way to measure hearing loss.” More sensitive testing might have provided more reliable information about smoking and hearing loss, she says.

None of the studies on this subject, including the new one, have found a clear reason why smoking may harm hearing. It's possible that toxins in cigarette smoke may damage the inner ear, Curhan said. Also, smoking can increase inflammation, and decrease blood flow to the cochlea, both of which can hurt the ear.

Protect Yourself From Hearing Troubles

The good news: Kicking the habit helps. The researchers found that study subjects' increased risk of hearing loss dropped significantly within five years of quitting. 

“Quitting smoking is crucial to your lung health, heart health, and more, and this study suggests it may be a reasonable step to take to reduce your risk of hearing loss as well,” Lipman says. (For advice on quitting, visit the Centers for Disease Control and Prevention’s website here.)

But it's also wise to take several hearing-protective steps that have lots of research backing them up. Number one on the list: Reducing your exposure to loud noises.

For instance, wearing earmuffs or earplugs in loud settings such as concerts can help, as can moderating your use of headphones. For more expert advice on how to prevent hearing loss, see our report. And if you have concerns about your hearing, see our hearing aids buying guide.