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As printed in Hearing Health, volume 19:3,
Fall 2003
Compiled By Mychelle Balthazard, M.P.H., contributing
editor
Maintaining the highest quality of life while living
with hearing loss can sometimes be difficult. Everyday
challenges include communication barriers, rising costs
of hearing care and dealing with symptoms of tinnitus,
dizziness, fatigue, etc., that sometimes accompany a
hearing impairment. People who proactively manage their
hearing loss and maintain good overall health seem to
be able to maximize the quality of their lives.
Part of the process is understanding how hearing may
be affected by injury and existing or newly acquired
illnesses and/or their treatment. The following summaries
provide a look at some of today’s major health
concerns that can cause or exacerbate hearing loss.
Cardiovascular Diseases
A cardiovascular disease (CVD) is a disorder of the
circulatory system that impairs the body’s ability
to move blood and nutrients to and from organs and cells.
The Centers for Disease Control and Prevention (CDC)
estimates that 61 million Americans have some type of
CVD.
Like most organs in our body, the ear relies upon
proper circulation to function well. The rich blood
supply of the cochlea needs constant replenishment and
is particularly susceptible to ischemia, the blockage
of a blood vessel. Fortunately this is rare.
Research has not yet produced a definitive link between
hearing loss and CVDs, which include hypertension, stroke,
heart failure, and many others, and/or CVD risk indicators
like smoking. But many scientists suspect a connection
and have conducted several studies aimed at uncovering
the relationships. For example, George Gates, M.D.,
published a study in 1993 showing a clear association
between low frequency age-related hearing loss and evidence
of CVD. Other research demonstrates a correlation between
sudden hearing loss and circulatory problems and between
tinnitus and cardiovascular problems.
In 1998, research led by Karen J. Cruickshanks, Ph.D.,
revealed that hearing loss is more common among individuals
who smoke cigarettes, one of the biggest contributors
to CVD. People who smoke carry a 70 percent greater
risk of having hearing loss in middle or old age than
those who do not smoke. But it remains unclear whether
or not the effects are independent of or related to
the ways smoking acts on the circulatory system, including
narrowing arteries, depleting blood of oxygen and increasing
blood pressure.
A few researchers have found a positive relationship
between hypertension (high blood pressure) and sensorineural
hearing loss but the data are controversial and very
few studies have addressed other factors that could
be at play.
What we do know for sure is that as research continues,
more pieces of the puzzle come together. Peter Torre,
III, Ph.D., presented findings at a 2002 meeting of
the American Heart Association concluding that participants
with a history of CVD were on average 54 percent more
likely to have impaired cochlear function than adults
without CVD. Torre’s data also indicate that there
is a greater chance of having debilitated cochlear function
among people who have had a heart attack.
A next step for this line of investigation is determining
which came first, the abnormal cochlear function or
the CVD, to confirm or rule out a possible causal relationship
between the two.
One interesting twist is related to drinking. Just
as it has been shown in some studies that low to moderate
alcohol intake can be beneficial for cardiovascular
function, low to moderate drinking seems to be beneficial
to hearing.
An Australian study conducted in the late 1990s demonstrated
that people who had the best hearing were the ones who
drank between two and four alcoholic beverages a day,
or at least had a small alcoholic intake per week. However,
more than four drinks a day had a negative effect on
hearing. Despite these results, the literature is not
fully conclusive on the subject and more research is
needed.
Cancer Treatments
In the U.S., approximately one out of every two men
and every three women will have some type of cancer
during their life, according to the American Cancer
Society. One of the most important decisions made following
a cancer diagnosis is how best to treat it. An individual’s
treatment plan will depend on the type and stage of
cancer and factors such as age, overall health status
and personal preferences.
For example, physicians and patients often must consider
and prepare for potentially harmful or unpleasant side
effects of any specific treatment. Hearing loss is among
the negative side effects of chemotherapy using the
common anticancer drugs cisplatin and carboplatin.
The chemicals used to make these drugs are toxic to
the delicate cochlea in the inner ear. The injury mechanism
appears to involve higher production of radical oxygen
species, or “free radicals,” that deplete
natural antioxidant substances. What follows is oxidative
stress and the beginning of cell death that in the cochlea
leads to hearing loss.
Recent data from studies using animal models and pre-clinical
trial research suggest that there may be a way to counteract
the damage and prevent hearing loss through the use
of vitamins, antioxidant compounds or other drugs. A
single preventive measure, perhaps in the form of a
pill, may be available in the near future.
Traumatic Brain Injury
It is estimated that a little more than 2 percent of
the U.S. population currently live with disabilities
resulting from brain injury. Severe blows or jolts to
the head that disrupt brain function often lead to continuing
health problems, such as headaches, seizures, blurred
vision, etc.
Trauma to the head – the location for all components
of our auditory system – commonly causes hearing
loss (sensorineural or conductive) and/or tinnitus,
balance problems and communication deficits. Blood in
the ear canal, injury to the middle ear or cochlea and
temporal lobe lesions are the usual roots of trauma-induced
hearing loss. Fluctuation in hearing may take place
throughout the first year after the traumatic incident.
Then hearing loss should stabilize.
HIV/AIDS
In the late 1980s, the medical community began to recognize
that HIV/AIDS could affect the auditory system. Estimates
of the number of people with AIDS that have some hearing
loss vary from study to study but range from 25 to 67
percent. Findings also suggest that 38 to 45 percent
of HIV-positive males have abnormal responses on testing
of their auditory brainstem response.
Although a relationship with hearing loss clearly exists,
the causes remain unknown. Some experts theorize that
because the virus attacks the immune system, people
with HIV/AIDS are far more susceptible to damage from
illnesses, including conductive hearing loss associated
with middle ear infections and sensorineural losses
from meningitis and cytomegolovirus. Other infectious
agents like syphilis and herpes that are more common
among people with HIV/AIDS also impair hearing. Finally,
similar to
the action of some anti-cancer drugs, the antiretroviral
drugs used to treat HIV/AIDS are toxic to the ear.
Ototoxic Pharmaceuticals
Approximately 200 medications are considered toxic to
the ear. The amount and type of damage they wreak on
the auditory system varies depending on the drug and
the individual. Some people experience mild reversible
hearing loss while many others never recover from impairments
that can be severe to profound. Tinnitus is also a common
outcome.
Salicylate analgesics (i.e., aspirin or products containing
aspirin) and non-steroidal anti-inflammatory drugs,
such as ibuprofen, are ototoxic when taken in high dosages
and over long periods of time. Hearing loss from these
families of pharmaceuticals is almost always reversible
once medication is discontinued.
Permanent hearing loss often accompanies treatment
with aminoglycoside antibiotics, including neomycin
and gentamycin, that are used to treat serious infections
or highly drug resistant bacteria. Other categories
known to be ototoxic include quinine, diuretics, anesthetics,
cardiac medications, glucocorticosteroids (cortisone,
steroids), mood altering drugs and certain vapors and
solvents. In some instances, exposure to loud noise
while taking certain medications will increase ototoxicity.
Special thanks to George A. Gates, M.D., DRF medical
director, for his review of this article.
For more information about these and other health conditions
and how they relate to hearing loss:
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