Cotinine not linked to hearing loss

Nov 16 2004

Levels of cotinine, a chemical that is made by the body from nicotine, which is found in cigarette smoke, does not appear to be linked to hearing loss, according to an article in the November issue of The Archives of Otolaryngology – Head & Neck Surgery.

According to the article, hearing loss is one of the most common conditions among adults 65 years and older. Several studies have linked cardiovascular disease with hearing loss, and others have shown that hearing loss may be affected by cigarette smoking, a known cardiovascular disease risk factor.

David M. Nondahl, M.S., of the University of Wisconsin-Madison, and colleagues investigated the relationship between levels of serum cotinine and hearing loss in 197 patients with new hearing loss and 394 patients without any hearing loss (aged 53-75 years) selected from the 2,800 participants in the five-year follow-up Epidemiology of Hearing Loss Study, 1998-2000. Serum cotinine levels were measured from blood samples obtained from the participants.

The researchers found no significant associations between serum cotinine levels and hearing loss. Among participants with hearing loss, 14 were current smokers, 96 were past smokers and 83 never smoked. Among participants with no hearing loss, 41 were current smokers, 183 were past smokers and 164 never smoked. Smoking information was not obtained for 10 participants.

“These results were not consistent with a previous report, which found cross-sectional associations between prevalent hearing loss and current smoking and environmental tobacco smoke exposure in the home. Longer-term longitudinal studies of smoking and/or serum cotinine levels and the subsequent development of hearing loss may help clarify these associations.”

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Exposure to Environmental Tobacco Smoke and Cotinine Levels — Fact Sheet

The National Institutes of Health's National Toxicology Program's 9th issue of the Report on Carcinogens listed ETS as a "known" human carcinogen, which indicates that there is a cause and effect relationship between exposure and human cancer incidence.

ETS is classified as a Group A carcinogen (known to cause cancer in humans) under the EPA's carcinogen assessment guidelines. Exposure to ETS causes lung cancer and has been linked to an increased risk for heart disease in nonsmokers.

ETS causes about 3,000 lung cancer deaths annually among adult nonsmokers. Scientific studies have also estimated that ETS accounts for as many as 35,000 deaths from ischemic heart disease annually in the United States. More research is needed to know exactly how recent changes in ETS exposure may affect lung cancer rates among adult nonsmokers.

ETS causes serious respiratory problems in children, such as greater number and severity of asthma attacks and lower respiratory tract infections. ETS exposure increases the risk for sudden infant death syndrome (SIDS) and middle ear infections for children.

Cotinine is a major metabolite of nicotine. Exposure to nicotine can be measured by analyzing the cotinine levels in the blood, saliva, or urine. Since nicotine is highly specific for tobacco smoke, serum cotinine levels track exposure to tobacco smoke and its toxic constituents.

In 1991, data showed that nearly 90 percent of the U.S. population had measurable levels of serum cotinine in their blood. The Centers for Disease Control and Prevention's National Report on Human Exposure to Environmental Chemicals found more than a 75 percent decrease in median cotinine (metabolized nicotine) levels for nonsmokers in the United States since 1991.

Children and teenagers, 3-19 years old, had higher levels of cotinine than did adults, 20 years old and above.

Involuntary exposure to ETS remains a common, serious public health hazard that is entirely preventable by adopting and enforcing appropriate regulatory policies. Smokefree environments are the most effective method for reducing ETS exposure. Healthy People 2010 objectives address this issue and seek optimal protection of nonsmokers through policies, regulations, and laws requiring smoke-free environments in all schools, work sites, and public places.

California, Connecticut, Delaware, Maine, Massachusetts, New York, and Rhode Island meet the nation's Healthy People 2010 objective to establish smoke-free indoor air laws covering public places and worksites. Because of comprehensive state laws, virtually all indoor workplaces in these states are now smoke free, including restaurants and bars.

The dramatic declines in serum cotinine levels among nonsmokers are a good indication that efforts to ensure clean indoor air through smoking restrictions in workplaces, restaurants and other public places are working. However, there are still too many people, especially young people, who continue to be exposed to environmental tobacco smoke (ETS).