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Smoking has long been accepted to be the cause of many chronic diseases and disabilities. Now, scientists have implicated tobacco in the hearing loss often associated with aging. s, unless you're a smoker, you did hear that correctly.

Hearing loss affects 30 to 35 percent of adults aged 65 to 75 years and yet little has been known about the root causes of this problem. Often written off to "aging," the impairment has now been directly linked to cigarette smoking. Also, diminished hearing was evident among smokers of all tested ages.

In what is considered to be a very large study, partly financed by the National Institute of Health, a team of scientists at the University of Wisconsin tested the hearing of a cross-section of 3,753 adult smokers and non-smokers. Subjects were all residents of Beaver Dam, Wisconsin, and ranged in age from 48 to 92. The researchers took a variety of measurements of hearing level, tone and conduction.

The study concluded that smokers were 1.7 times as likely to suffer hearing loss as non-smokers. The odds of experiencing substantial hearing loss increased with the number of "pack-years." (Pack-years are the number of cigarettes smoked daily, divided by 20 and then, multiplied out for the total number of years the subject was a smoker.) Risk of hearing loss was also shown to be higher for non-smokers who live with at least one smoker; second-hand smoke damages hearing (and causes numerous diseases).

Although the six scientists did not set out to establish the process by which tobacco affects auditory loss, they pointed to two possible factors. First, the researchers suggested that smoking reduces the body's natural antioxidant mechanisms. In other words, it interferes with the body's ability to get rid of free radicals or "oxidants"–microscopic garbage that bombards our cells daily throughout life. Free radicals are unstable molecules created by normal metabolic processes and which are electrically charged and highly reactive with other substances in the body. It is this "oxidation," or garbage buildup, that is associated with DNA changes and the cellular damage we call aging. Normally, antioxidants¡ª such as vitamin C or selenium¡ªsweep away many of these dangerous bits before they are able to cause excessive impairment of the body's healthy cells.

The second way smoking causes hearing deficit is by reducing the vascular supply to the auditory system. Put simply, less blood gets to the ear mechanism and eventually, hearing is damaged.

Undeniable Connection

Cigarette smoking can be traced to a number of other lifestyle and socio-economic factors that may adversely affect health and therefore, indirectly affect hearing loss. For example, people who smoke may be more likely to expose themselves to workplaces and leisure areas where the noise levels are significantly higher; they may be more likely to consume alcoholic beverages; or they may have chronic conditions such as heart disease which may be associated with hearing loss.

Some say smokers may be less likely to take nutritional supplements or consume a healthy, organic diet. The study was designed to filter out any possible "confounding" effects of these other lifestyle elements. Also, researchers adjusted for other factors such as gender, age and education. Still, strong association between smoking and hearing loss remained statistically undeniable, even after adjusting for other potential environmental, diet and social links.

"Every year, we discover more and more serious conditions caused by smoking, including passive smoking... vision, cataracts, macular degeneration ...the list goes on and on," says Dr Roberta Ferrence, director of the Ontario Tobacco Research Institute and senior scientist with the Centre for Addiction and Mental Health.

If further population-based clinical studies confirm these conclusions, "modification of smoking habits may prevent or delay age-related declines in hearing sensitivity," suggests the group report. But you may want to turn to nutritional supplements to actually offset hearing damage.

Reversing the Loss

Is it possible to reverse the damage to hearing caused by noise, aging and environmental factors?

Possibly, suggests Colonel Richard D. Kopke, a physician with the United States Army Medical Corps. Jytuitary researchers have developed a technique that may be able to restore health to sensitive hair cells within the ear that are thought to be irreparably damaged during hearing impairment.

Of the 30 million North Americans who have some degree of hearing loss, 30 percent, or nine million people, have been at least partly deafened by excessive noise. The pressure and vibrations of loud noises including jet engines, music, gunfire–or it has now been found, smoking–can cause cells to generate microscopic garbage that bombards and alters other substances in the body such as hearing-related hair cells. Called "free radicals," these free-floating and unstable molecules are electrically charged and highly reactive, causing cell death and permanent injury. It is this oxidation or garbage build-up that is associated with DNA changes and with the cellular damage often thought of as the aging process.

Antioxidants such as vitamins A, C, E, beta-carotene, selenium and other nutrients have the ability to latch onto some of these dangerous free radicals before they can cause excessive injury to healthy cells. Dr Kopke and his colleagues have designed a way to thread a tiny catheter through the outer ear, under the eardrum and to themembrane at the end of the cochlea. The catheter is then used to deliver powerful antioxidants directly to the area every two to three days, for two weeks.

This may help, suggests the researcher, by mopping up some of the free radicals in the hearing mechanism. Kopke says that antioxidant supplements could be taken orally prior to exposure to unavoidable loud noise, to help prevent hearing loss. Implied is the recommended use of antioxidants by smokers. In the meantime, Kopke recommends wearing hearing protection when around loud noises; and the use of common sense. However, for those concerned about age-related hearing loss, "common sense" may now have to include the avoidance of cigarette smoke, including secondhand smoke.

Michael Downey is a Toronto-based writer and editor, and a co-founder of the Coalition Against Water Fluoridation.

Source: alive #210, April 2000