Chronic tinnitus is present frequently or continuously. The National Institute on Deafness and Other Communication Disorders defines chronic tinnitus as occurring for more than three months. The number of people with chronic tinnitus is 5 to 10 percent of the U.S. adult population, with about 0.5 percent having severe, debilitating tinnitus. Chronic tinnitus occurs in men and women, in the young and the old, and in people from all walks of life. In this article, and the Summer 2013 special issue of Hearing Health magazine, our topic is chronic tinnitus.
What Causes Tinnitus?
Tinnitus is more common in men, seniors, blue-collar workers, and people with certain common health problems (arthritis, hypertension, varicose veins, and arteriosclerosis). But all of these associations are probably explained by one simple correlation: The worse your hearing is, the more likely you are to have tinnitus.
It doesn’t seem to matter very much whether the hearing problem is in the inner ear or the middle ear, or what otologic disorder has caused it. Roughly 90 percent of tinnitus cases occur with an underlying hearing loss.
Most hearing loss develops gradually during middle or old age, without any identifiable cause or association other than advancing years.
Age-related hearing loss, or presbycusis, can occur whether or not someone has experienced significant noise exposure, ear infections, or any other specific ear disease. Presbycusis continues to progress with age and is usually more severe in men than in women of the same age. As a result, we may expect the prevalence of tinnitus to be higher in men and to increase with age. Indeed, this is uniformly found in epidemiological surveys.
These same surveys generally show that the next most important risk factor for hearing loss and tinnitus, after age and gender, is excessive noise exposure. It is generally true that the louder the noise and the longer the exposure, the greater the hearing loss.
People who have regular and prolonged exposure to noise, usually at work (such as in construction), begin to be at risk of permanent hearing loss and tinnitus at levels of about 85 decibels (dB), which is roughly equivalent to the sound of heavy city traffic. At this level, most people would need to speak very loudly or even to shout to converse with someone only at arm’s length away.
Outside of the workplace, one of the most important sources of harmful noise exposure is recreational shooting. But any noise exposure that causes temporary tinnitus or muffled hearing can, if regularly repeated, lead to permanent hearing loss and tinnitus. This includes unsafe listening to personal MP3 players.
There are also many ear disorders other than age-related and noise-induced hearing loss that cause hearing loss and tinnitus.
Sensorineural (inner ear) hearing loss can be caused by genetic mutations, by some drugs used to fight infection and cancer, or by head injuries. Conductive (middle ear) hearing loss is often caused by chronic ear infections or otosclerosis, a hereditary middle ear disease.
In developed countries, sensorineural hearing loss is much more important than conductive hearing loss as a cause of tinnitus, and most sensorineural loss is in turn associated with loss of inner ear hair cells.
At present, hair cell loss in humans is considered permanent, but research in hair cell regeneration may someday make it possible to both restore hearing and eliminate tinnitus for people with sensorineural hearing loss. (For more about the effort to regenerate hair cells in humans, see “Two Problems, One Solution
What Does Tinnitus Sound Like?
Patients who complain of tinnitus usually describe their sounds as ringing, buzzing, humming, and whistling. Some mention hissing, crickets, roaring, and falling water.
Just as the prevalence of tinnitus is related to the presence and severity of hearing loss rather than to particular otologic disorders, the quality of tinnitus (how it sounds) is generally unrelated to specific diagnosis.
Patients can compare their tinnitus sounds to tones and noises produced by audiometric equipment. This is called matching. Most say their tinnitus pitch is closest to tones or noises with central frequencies above 3,000 hertz (Hz). Match frequency correlates, in general, with hearing loss severity and configuration. Patients with low-pitched tinnitus (under 1,500 Hz) tend to have much more severe hearing losses, especially in the low frequencies, than do patients with higher-pitched tinnitus.
When a tone or noise of about the right pitch is varied in intensity until it is just as loud as the patient’s tinnitus, the matching intensity is usually found to be less than 10 dB above the patient’s threshold at that frequency.
What Is the Effect of Tinnitus?
Fortunately, most people with chronic tinnitus are not too bothered by it. Many people never seek medical attention for their tinnitus, and many who see a doctor only want to know that their tinnitus is not a harbinger of serious disease or impending deafness.
On the other hand, many patients (tinnitus “sufferers”) are very much bothered by their tinnitus. They may say that it is annoying, intrusive, upsetting, and distracting. It prevents some patients from carrying out certain critical activities in their daily lives.
However, it has been impossible to predict from tinnitus sensation—its loudness, pitch, and quality—whether or not a person will be a tinnitus sufferer. While tinnitus sufferers often describe their tinnitus as very loud, their matching levels are not significantly different from those measured for patients with non-bothersome tinnitus.
Tinnitus sufferers who were members of a small tinnitus self-help group were asked to list difficulties they have had as a result of the tinnitus. Among the 72 who responded, the most frequently reported problems were:
Getting to sleep (57 percent)
Persistence of tinnitus (49 percent)
Understanding speech (38 percent)
Despair, frustration, or depression (36 percent)
Annoyance, irritation, or inability to relax (35 percent)
Poor concentration or confusion (33 percent)
Most other descriptive studies of suffering related to tinnitus have come to similar conclusions. Self-reported tinnitus problems tend to cluster into the categories of sleep, hearing, emotion, and concentration.
The persistence of the tinnitus seems to be key. Many patients state that their tinnitus is not particularly unpleasant except for the fact that, like a dripping faucet, it will not go away. Concerns that the tinnitus is a sign of something serious, won’t go away, or cannot be eliminated or controlled can make it difficult for some people to ignore their tinnitus, leading to problems with sleep, concentration, and emotion.
The hearing difficulties tinnitus sufferers report are considered to be attributable to their hearing loss rather than to the tinnitus itself.
Also, many tinnitus sufferers complain of difficulty tolerating external sounds of even moderate intensity, a condition called hyperacusis.
Why do some people with tinnitus become tinnitus sufferers, while others do not? Psychological factors present before the onset of tinnitus may be very important. Many, if not most, patients with really bothersome tinnitus are found to have a major depressive disorder. About half of depressed tinnitus patients reported previous episodes of depression, before they ever noticed their tinnitus.
Will the Tinnitus Get Better?
Clinicians are routinely asked by their patients whether their tinnitus will get better, get worse, or stay the same. Unfortunately, there has been far too little good research to guide our answers. Retrospective clinic-based studies—asking tinnitus patients how their tinnitus has changed over time—tend to suggest that more patients get worse than get better. But these studies are flawed by selection bias: Patients whose tinnitus has improved spontaneously are much less likely to seek care and are thus less likely to be included in the research.
One population-based longitudinal study of 153 Swedes who had been followed from ages 70 to 79 found, as expected, that the prevalence of continuous or occasional tinnitus increased from age 70 (31 percent) to age 79 (44 percent). Interestingly, the majority of these patients who had reported continuous tinnitus at age 70 reported only occasional tinnitus or no tinnitus at all by age 79, suggesting that some older patients experience spontaneous remissions or improvements.
Even more striking is the lack of data pertaining to prognostic factors. We simply don’t know how to predict which patients are likely to do well and which patients will do poorly without treatment. Factors like age, gender, educational level, initial severity, and duration may predict outcome, but currently these are unknown.
Lacking better research data, most clinicians rely on their own clinical experience. I have found that after one year, major spontaneous changes in tinnitus patients are infrequent, but that over time people are more likely to get better (suffer less) than to get worse.
Most tinnitus treatments aim to attack either the tinnitus sensation (the sounds that people hear) or the tinnitus suffering (the ways that tinnitus affects people). No treatment has been shown to frequently eliminate tinnitus, or even to be more effective than a placebo.
Treatments such as sound therapy are aimed at the tinnitus sensation (making the tinnitus less audible). Conversely, some treatments such as counseling aim squarely at tinnitus suffering and make no attempt to change the tinnitus sensation. This does not necessarily mean that treatments aimed at tinnitus suffering are better than those aimed at tinnitus sensation. It does mean that unless tinnitus sensation can be completely eliminated, treatment outcomes should be measured in terms of reduction of suffering.
And here we have a problem: There is so far no consensus among clinicians or clinical scientists regarding the best ways to measure tinnitus suffering. This makes it more difficult to assess and compare various treatments.
Our lack of understanding of the natural history of tinnitus makes randomized clinical trials essential to prove the value of tinnitus treatments. That said, there are many treatments available, each with varying levels of success. This special issue of the magazine covers the major, research-based options currently available.
In the meantime, because of the huge overlap between hearing loss and tinnitus, a biologic approach that can solve the issue of hearing loss through hair cell regeneration may be the best bet for many tinnitus sufferers.
Robert A. Dobie, M.D., is a clinical professor of otolaryngology at the University of Texas, San Antonio, and the University of California, Davis. As a partner in Dobie Associates, he provides consultation in hearing, balance, hearing conservation, and ear disorders. Dobie’s research interests include age-related and noise-induced hearing loss and tinnitus. He is the author of more than 190 publications.
This article is adapted from “Overview: Suffering From Tinnitus,” by Robert A. Dobie, M.D., a chapter in “Tinnitus: Theory and Management,” edited by James B. Snow, Jr., M.D. It appears with permission from Dobie, Snow, and PMPH-USA, the publisher.