|
At first glance, the heart and the cochlea seem to have little in common. One supplies a constant supply of freshly oxygenated blood to all the tissues and organs within the body while the other codes pressure fluctuations into information interpreted by the brain as sound. Since each organ is placed at risk when the blood supply is interrupted or decreased, risk factors for heart disease and hearing loss are often shared.
Such common risk factors include but are not limited to the following:
· Smoking;
· High blood cholesterol;
· High blood pressure;
· Diabetes;
· Obesity.
Let's look at some hearing research suggesting that the above modifiable risk factors affect the cochlea as well as the heart, probably due to their damaging effects upon blood vessels and oxygen levels within each organ:
Smoking
Smoking is an addiction that harms nearly every organ of the body, causing many diseases and reducing the health of both smokers and nonsmokers, who inhale unwanted secondhand smoke.
According to researchers at Western Michigan University, smokers are at greater risk for cochlear damage than their nonsmoking counterparts even when hearing thresholds are as yet unaffected.1 Their study used DPOAEs, a measure of outer hair cell activity, to assess the effects of smoking on cochlear function. Twenty-four healthy adults, 12 smokers and 12 nonsmokers in the 20-30-year age range, were selected based on self-reported histories of 5 to 8 years of smoking or nonsmoking, respectively.
Conventional and ultra-high frequency audiometry showed normal or age-appropriate thresholds across both groups. However, DPOAE results showed small but significant declines in smokers; I/O detection thresholds were also significantly elevated at high frequencies in smokers. Researchers concluded, "DPOAE amplitudes and I/O detection thresholds may identify early changes in cochlear function in smokers."
High Blood Cholesterol
Cholesterol is a waxy, fat-like substance produced in the liver and important as a constituent of cell membranes, including "fine tuning" the motor function of the outer hair cells.
Hypercholesterolemia or "high blood cholesterol" is of concern primarily because of its damaging effects on the cardiovascular system, but Turkish researchers further studied the effects of the condition on the cochlea of 20 guinea pigs with high blood cholesterol induced by diet as compared with 20 guinea pigs fed a normal diet.2 After 4 months, the basal and apical turns of the cochlea were examined by light microscopy and transmission electron microscopy.
Researchers write, "The control group showed normal cochlear ultrastructures consistent with normal thresholds, whereas the cholesterol group had profound edema in the strial marginal layer and slight edema in the outer hair cells, in line with data from auditory brainstem responses revealing changes in hearing sensitivity in various degrees." Such findings led the researchers to conclude, "Hypocholesterolemia alone may cause auditory dysfunction if dietary cholesterol is kept at a high level for a long time."
High Blood Pressure
High blood pressure, or hypertension, affects about one in three adults in the U.S., but many are unaware of it because this dangerous health condition generally has no symptoms.
Mexican researchers studied the effects of systemic high blood pressure on the cochlea with audiometry and DPOAEs.3 Results showed deterioration of hearing thresholds at 8 kHz in patients with arterial hypertension as compared to control patients; in addition, the hypertensive patients showed a higher frequency of abnormal DPOAEs. They concluded, "Patients with systemic arterial hypertension may have cochlear dysfunction associated with the vascular disease..."
Diabetes
Diabetes is a disorder in which the body does not produce or properly use insulin, leading to damaging high blood-sugar levels.
Researchers at the Rochester Institute of Technology looked at hearing loss in older Type II diabetics and found that "the majority of differences between the hearing abilities of the aged diabetics and their age-matched controls were found in pure-tone audiograms, wideband noise and speech reception thresholds, and otoacoustic emissions."4 The greatest deficits tended to be at low frequencies, with a "strong tendency for diabetes to affect the right ear more than the left." Elevated blood sugar levels were suggested as a possible underlying physiological mechanism for such hearing loss.
Obesity
Obesity, or excess body fat of 30 pounds or more, is a growing problem that affects up to 30 percent of the U.S. population.
Belgian researchers studied medical risk factors contributing to age-related hearing impairment in over 4,000 subjects between 53 and 67 years of age.5 Pure-tone averages (PTAs) were collected and participants filled out a questionnaire on environmental risk factors and medical history. Among other factors, researchers found that a "high body mass index (BMI) correlated with hearing loss across the frequency range tested" and suggested, "A healthy lifestyle can protect against age-related hearing impairment."
Modifying Risk Factors
To positively modify the risk factors listed above, which may affect both the heart and the cochlea, WebMD recommends the following beneficial steps:6
· Quit smoking, or better yet, don't start.
· Improve cholesterol levels through a diet low in cholesterol and saturated and trans fat. Regular exercise will also help lower "bad" cholesterol and raise "good" cholesterol. Medications are often needed to reach cholesterol goals.
· Control high blood pressure through diet, exercise, weight management, and medications if needed.
· Control diabetes through a healthy diet, exercise, maintaining a healthy weight and taking medications as prescribed.
· Get active by exercising at least 30 minutes a day, at moderate intensity, on most days. More vigorous activities are associated with more benefits.
· Eat right, with a diet low in sodium, saturated fats, trans fat, cholesterol and refined sugars. Also eat plant-based foods such as fruits and vegetables, nuts and whole grains.
· Achieve and maintain a healthy weight by exercising and eating right.
· Manage stress by practicing relaxation techniques, learning how to manage your time, setting realistic goals, and trying some new techniques such as guided imagery, massage,Tai Chi or yoga.
Good advice for you and your patients to share a healthy heart and cochlea.
References
1. Negley, C, Katbamna, B, Crumpton, T, et al. (2007). Effects of cigarette smoking on distortion product otoacoustic emissions. Journal of the American Academy of Audiology, 18(8): 665-74.
2. Satar, B, Ozkaptan, Y, Surucu, HS, et al. (2001). Ultrastructural effects of hypercholesterolemia on the cochlea. Otology & Neurotology, 22(6): 786-9.
3. Esparza, CM, Jauregui-Renaud, K, Morelos, CM, et al. (2007). Systemic high blood pressure and inner ear dysfunction: a preliminary study. Clinical Otolaryngology, 32(3): 173-8.
4. Frisina, ST, Mapes, F, Kim, S, et al. (2006). Characterization of hearing loss in aged type II diabetics. Hearing Research, 211(1-2): 103-13.
5. Fransen, E, Topsakai, V, Hendrickx, JJ, et al. (2008). Occupational noise, smoking, and a high body mass index are risk factors for age-related hearing impairment and moderate alcohol consumption is protective: A European population-based multicenter study. Journal of the Association for Research in Otolaryngology, 9(3): 264-76,
6. Heart disease: Risk factors for heart disease. WebMD. Accessed online at www.webmd.com/heart-disease/risk-factors-heart-disease?print=true
Jess Dancer is professor emeritus of audiology at the University of Arkansas at Little Rock and can be contacted at jedancer@ualr.edu.
|