Ashley W. Harkrider
aharkrid@utk.edu
Craig A. Champlin
University of Tennessee
Department of Audiology and Speech Pathology
457 South Stadium Hall
Knoxville, TN 37996
Popular Version of Paper
4pPP7
Friday Afternoon, June 2
139th ASA Meeting, Atlanta, GA
Prevalence of Nicotine:
Fifty million Americans smoke cigarettes regularly, many are on nicotine-replacement
therapies in an attempt to stop, and nicotine is being used experimentally
for treatment of diseases, including Alzheimers, Parkinsons, attention
deficit hyperactivity disorder, schizophrenia, and Tourettes syndrome.
Due to the increased use, there has been a dramatic escalation in the study
of nicotine's effects in humans. Regardless of this, there is still
much to learn about the effect of nicotine on hearing. Most experiments
involving human subjects have used cigarette smoking to study these effects.
Unfortunately, it is difficult to determine whether effects seen in studies
involving smoking are due to primary components, such as nicotine, or a
combination of other components that make up a burning cigarette (e.g.,
carbon monoxide). Perhaps for this reason, previous findings on smoking
and human hearing have not agreed. Some studies showed that chronic
smoking decreased overall hearing sensitivity, some showed that it improved
processing of certain sounds, and some showed no effect.
Present study:
In the present study we attempted to develop a systematic and non-invasive
way to evaluate the influence of nicotine on sound traveling from the ear
to the brain in humans. By applying electrodes to the scalp, we were
able to measure changes in electrical activity from different levels of
the auditory system in response to sound. By measuring these changes
in the presence and in the absence of nicotine, we made deductions about
the contributions of nicotine to the transmission of auditory information.
Our subjects were non-smokers in an attempt to avoid the potential influences of long-term factors associated with nicotine use and smoking (e.g., continual tolerance, withdrawal) and to avoid non-nicotine factors associated with smoking (e.g., carbon monoxide, carbon dioxide, nitrogen, tar). We used a low-dose patch that delivered nicotine through the skin (transdermal patch) because it administers a relatively steady concentration of nicotine for dependable periods of time. The lowest dose is fairly well tolerated by non-smokers but still provides smoking doses of nicotine. In the control session, changes in electrical activity in response to sound were recorded from the scalp after a transdermal patch with no nicotine had been placed on the arm of the subject. In the experimental session, the same changes in electrical activity were recorded after the subject had received a transdermal patch with nicotine. The electrical activity recorded by the electrodes during the control session was compared to that obtained during the nicotine session.
Findings of present study:
Nicotine appeared to improve the travel of sound from the ear to the
brain, while at the same time reducing the auditory systems response to
repetitive, distracting sound. So, it seems that nicotine increases
auditory awareness and improves the efficiency of auditory processing.
The greatest effect of nicotine was seen in responses generated from regions
of the auditory system near to, and including, the brain.
It appears that low doses of nicotine given over a short period of time affect responses in non-smokers similarly to the way cigarette smoking affects responses from smokers. This suggests that the effects that were seen in auditory studies involving smokers may be primarily due to nicotine and not to other compounds generated by smoking.
It should be noted that this is an exploratory study, involving the examination of the short-term effects of nicotine on a large number of measures. More focused studies must be done before definite conclusions about the role of nicotine on human hearing can be made. Although the short-term effects of nicotine on human hearing appear to be positive in this study, the long-term effects have been reported by some to be unfavorable. Further, many of the effects of nicotine on the human body have been shown to be harmful.
During the meeting, the presenter may be contacted at the Westin Peachtree Plaza Hotel.