Cigarette smoking as a risk factor for auditory problems

Association of Smoke and Nicotine Product Consumption With Sensorineural Hearing Loss: A Population-Level Analysis

OBJECTIVE

To test the hypothesis that use of cigarettes or other products with either cigarette-like smoke profile or high nicotine content by young populations increases the odds of developing sensorineural hearing loss (SNHL).

STUDY DESIGN

Retrospective cohort study.

SETTING

TriNetX US Collaborative Network (2003-2022).

PATIENTS

Approximately 3.6 million patients at least 18 years old.

INTERVENTION

None.

MAIN OUTCOME MEASURES

The primary outcome of interest was diagnosis of SNHL, defined using medical billing codes ( International Classification of Diseases, Tenth Revision , Current Procedural Terminology , etc.). Cohort inclusion criteria included electronic health record entry after 2003, age 18 to 54 or 55+ years at index, and status of cigarette, noncigarette nicotine, or cannabis use. Covariates were controlled via 1:1 propensity score matching for SNHL-related conditions, including diabetes mellitus and ischemic diseases. Odds for developing SNHL were calculated against control subjects aged 18 to 54 years who have no record of nicotine/cannabis use.

RESULTS

Odds for developing SNHL are higher for people 18 to 54 years old who use any nicotine product (odds ratio [95% confidence interval], 5.91 [5.71-6.13]), cigarettes only (4.00 [3.69-4.33]), chewing tobacco only (9.04 [7.09-11.63]), or cannabis only (3.99 [3.60-4.44]) compared with control. People 55+ years old who use no products also showed increased odds for SNHL (4.73 [4.63-4.85]).

CONCLUSIONS

Both nicotine and smoke exposure seem to be strongly associated with increased odds for developing SNHL, with chewing tobacco having the strongest association.

Occurrence of changes in the auditory evoked potentials of smokers: systematic review of the literature

PURPOSE

To verify the occurrence of abnormal auditory evoked potentials (AEP) tests in adult smokers.

RESEARCH STRATEGIES

Systematic review of the literature according to the PRISMA guidelines, to answer the question: "Are there any changes in the AEP results in adult smokers?", PECOS strategy. Research carried out on PubMed, Embase, CINAHL, LIVIVO, Scopus, Web of Science, LILACS and Scielo databases. Additional search of gray literature: Google Scholar and ProQuest hand searching of reference lists of the included studies.

SELECTION CRITERIA

Cross-sectional studies were selected, without restriction on the year of publication and language.

DATA ANALYSIS

First, the titles and abstracts of all the studies were analyzed, followed by the full reading of the eligible studies.

RESULTS

898 articles were collected, after the duplicate studies were removed and after blind analysis by three researchers, 8 studies of the observational type were selected. Most studies have found an association between active smoking and changes in electrophysiological tests.

CONCLUSION

Normal hearing adult smokers present alterations in short and long AEP. In the auditory brainstem response, the main altered components were the increase in waves latencies of I and III and in the interpeaks I - III and III - V, as well as a decrease in the amplitude of the waves. In Mismatch Negativity, there was a significant increase in wave amplitude and latency. In the long latency potential, P300, there was an increase in latencies and decreased amplitudes in the components N1 (in Fz) and P3.

Prevalence of Tinnitus and Its Associated Factors in the PERSIAN Guilan Cohort Study

Introduction

Tinnitus can be associated with many auditory and non-auditory factors, and its prevalence varies widely in the literature. There is no large sample of published data on tinnitus prevalence and its associated factors in Iran. Here, we analyzed the PERSIAN Guilan Cohort Study (PGCS) data and reported the prevalence of tinnitus and some of the risk factors related to tinnitus in the Iranian population.

Materials and Methods

This cross-sectional study was conducted on 10520 men and women between 35 and 70 years old. The prevalence of tinnitus and associations between tinnitus and age, sex, habitat, marital status, employment status, socioeconomic status, educational level, lifestyle habits, and comorbid diseases were examined using simple and multiple logistic regression analyses.

Results

The prevalence of tinnitus was 6.4% in this study. Based on the adjusted analysis, only older age (odds ratio: 2.60, 95% confidence interval: 1.88 - 3.60), residency in a rural area (odds ratio: 1.22, 95% confidence interval: 1.03 - 1.44), cigarette smoking (odds ratio:1.33, 95% confidence interval: 1.04 - 1.72), and having other comorbidities (odds ratio: 2.75, 95% confidence interval: 2.19 - 3.44) were related to tinnitus. In addition, the results of subgroup analyses by sex were mostly consistent with the overall analysis.

Conclusions

Our results revealed that the prevalence of tinnitus in the north of Iran is comparable with other communities. Age and other comorbidities were among the most related factors to tinnitus.

Efferent Auditory Pathways Inhibition in Turner syndrome

PURPOSE

The goal of this study is to investigate the efferent auditory pathways inhibition in Turner's syndrome and to relate it to the cytogenetic profile.

METHODS

This is a cross-sectional study with a comparison group. A sample with 94 participants divided into two groups: The study group was a sample of 40 patients diagnosed with Turner's syndrome (17.6 years of age). The control group was composed of 54 volunteers (18.9 years of age), female, without syndrome. The selected individuals were submitted to efferent auditory pathways inhibition research.

RESULTS

The mean of the inhibitory effect of the efferent auditory pathway in the study group in the right ear was 0.4 dB and in the comparison group it was 1.9 dB, however in the left ear the mean of the inhibitory effect of the efferent auditory pathway was 1.4 dB in the study group and 0.8 dB in the comparison group. The inhibitory effect of the efferent auditory pathway was present in 14 individuals with monosomy and in 15 with other cytogenetic alterations.

CONCLUSIONS

In the study group, the efferent auditory pathways inhibition value was significantly higher in the left ear and significantly lower than the control group in the right ear. There was no significant difference in efferent auditory pathways inhibition of right ear and left ear between the karyotype types.

Self-Reported Drug Use and Hearing Measures in Young Adults

Purpose The purpose of this study was to examine marijuana or other substance use on pure-tone thresholds and distortion product otoacoustic emissions (DPOAEs) in young adults. Method Young adults (n = 243; 182 women, 61 men; M _age = 20.9 years, SD = 2.7 years) participated in this study. Survey data included personal music system use, marijuana use, and misuse of prescription medications. Otoscopy, tympanometry, pure-tone audiometry, and DPOAEs were obtained. Pure tones from octave frequencies of 0.25 through 8 kHz were obtained, and DPOAEs were recorded between f₂ frequencies of 1 and 6 kHz using two continuously presented stimulus tones swept in frequency. Results Those who reported marijuana or stimulant use had similar pure-tone averages (0.5, 1, 2, and 4 kHz) compared to those who reported never using marijuana or stimulants. Women who reported marijuana use in the past 30 days > two times had statistically significant higher mean DPOAEs compared to women who reported ≤ two times or no marijuana use in the past 30 days. Men, however, who reported marijuana use in the past 30 days > two times had lower, but not statistically significant, mean DPOAEs compared to men who reported ≤ two times or no marijuana use in the past 30 days. Women who reported ever using stimulants had statistically significant higher mean DPOAEs compared to women who reported never using stimulants; for men, mean DPOAEs were similar between those who reported ever using stimulants and those who never used stimulants. Conclusions The results of this study demonstrate different and contradictory associations between marijuana use, stimulant use, and hearing outcomes as a function of sex. Future research is needed to explore these associations utilizing larger sample sizes while accounting for additional harmful exposures to other noise exposures.

Behavioral Hearing Thresholds and Distortion Product Otoacoustic Emissions in Cannabis Smokers

Purpose Cannabis is a widely used drug both medically and recreationally. The aim of this study was to determine if cannabis smoking is associated with changes in auditory function, as measured by behavioral hearing thresholds and/or distortion product otoacoustic emissions (DPOAEs). Method We investigated hearing thresholds and 2f₁-f₂ DPOAEs in 20 cannabis smokers and 20 nonsmokers between 18 and 28 years old. Behavioral thresholds were obtained from 0.25 to 16 kHz. DPOAEs were measured using discrete tones between f₂ of 0.5 and 19.03 kHz using an f₂/f₁ ratio of 1.22 and L₁/L₂ = 65/55 dB SPL. Thresholds and DPOAE amplitudes were compared between groups using linear mixed-effects models with sex and frequency as predictors. Results Behavioral thresholds in smokers did not differ significantly between smokers and nonsmokers (all ps > .05). Although not significant, long-term smokers exhibited poorer thresholds than short-term smokers and nonsmokers. Smokers generally exhibited lower DPOAE amplitudes than nonsmokers, although the differences were not significant. Male smokers had significantly poorer DPOAE amplitudes than male nonsmokers in the low frequencies (f₂ ≤ 2 kHz; p = .0245). Conclusion Results indicate that smoking cannabis may negatively alter the function of outer hair cells in young men. This subtle cochleopathology is evident in the absence of measurable differences in behavioral hearing thresholds between cannabis smokers and nonsmokers.

The effect of simultaneous exposure to cigarette smoke and noise on distortion product otoacoustic emissions in rats

Cigarette smoking is a possible risk factor for hearing loss. However, the impact of simultaneous exposure to noise and smoke on hearing has remained controversial. This study investigated the combined effect of exposure to cigarette smoking and noise on hearing loss. Three groups of male Wistar rats (275 ± 25 g) were subjected to white noise (102 ± 0.5 dB), cigarette smoking (20 cigarettes), and both cigarette smoking and noise for 8 h and 10 days inside the exposure chamber. The control group was exposed to neither noise nor smoke. Distortion product otoacoustic emissions (DPOAE) were measured before any intervention, and it was repeated 1, 7, and 21 days after the last exposure. One-day postexposure to noise, cigarette smoking, and both cigarette smoking and noise, the mean of DPOAE amplitudes decreased significantly ( p < 0.05) between, respectively, 5.7-30.7, 1.5-7.5, and 5.2-32.6 dB within the frequency range of 4620-9960. Temporal DPOAE change in rats exposed to noise or both cigarette smoking and noise was not significantly different ( p > 0.05). DPOAE amplitudes returned to the baseline values in the group subjected to smoking 21 days postexposure. The most permanent change was observed in rats exposed to both cigarette smoking and noise. Accordingly, simultaneous subacute exposure to noise and cigarette smoking increases the effect of noise on permanent hearing loss. Therefore, smoking workers exposed to noise might be at a greater risk of developing hearing loss, and it is recommended that authorities in charge take note of this evidence.

Otorhinolaryngological symptoms among smokeless tobacco (Maras powder) users

OBJECTIVE:

This study aims to investigate the relationship between smokeless tobacco (maras powder) consumption and otorhinolaryngological symptoms.

METHODS:

This descriptive study was carried out on 599 participants. The participants were divided into two groups. Of these, 299 (49.9%) patients aged over 18 years were the first group; they used smokeless tobacco for at least 5 years. The remaining patients comprised the second group, which included 300 (50.1%) healthy volunteers who did not use tobacco or its products and demonstrated some similarities with the first group. For the purpose of data collection, a questionnaire consisting of 45 questions was administered to the participants.

RESULTS:

Cough, sputum, shortness of breath, dysphagia, snoring, and apnea-hypopnea were found to be significantly increased in smokeless tobacco users. The highest odds ratio (OR) found was for sputum at 2.615. Similarly, other oral cavity symptoms such as mouth tickling, dryness of throat, mouth sores, halitosis, taste disorders, and toothache were found to be significantly increased in smokeless tobacco users. It is noteworthy that halitosis was 9.4 times more prevalent among smokeless tobacco users than in the non-tobacco users. Sinonasal symptoms such as sneezing, headache, facial fullness, and anorexia were found to be significantly increased in smokeless tobacco users. However, there were no differences between the groups in terms of ear symptoms.

CONCLUSION:

This study demonstrated that the negative effects of smokeless tobacco consumption were particularly higher in the oral cavity, which in turn gave rise to a number of serious upper respiratory tract complaints.

Is smoking a risk factor for tinnitus? A systematic review, meta-analysis and estimation of the population attributable risk in Germany

OBJECTIVE

To assess the epidemiological association of smoking status and tinnitus with a systematic review and meta-analysis and to estimate the population attributable risk in Germany.

DATA SOURCES

A systematic literature search in PubMed and ISI-Web of Science Core Collection resulted in 1026 articles that were indexed until 15 September 2015. Additionally, proceedings of the international tinnitus seminars and reference lists of relevant articles were screened.

STUDY SELECTION

Two reviewers searched independently for epidemiological studies. Tinnitus as a manifestation of tumours, vascular malformations, specific syndromes or as a consequence of surgical and medical treatment was not considered. Moreover, studies conducted among patients of ear, nose and throat clinics were excluded.

DATA EXTRACTION

If only raw data were provided, effect sizes were calculated. Further unpublished data were received by corresponding authors.

DATA SYNTHESIS

Data of 20 studies were pooled. Current smoking (OR 1.21, 95% CI 1.09 to 1.35), former smoking (OR 1.13, 95% CI 1.01 to 1.26) and ever smoking (OR 1.20, 95% CI 1.11 to 1.30) were significantly associated with tinnitus. Moreover, sensitivity analyses for severe tinnitus (OR 1.32, 95% CI 1.10 to 1.58) and for studies of superior quality (OR 1.15, 95% CI 1.03 to 1.29) showed increased risks. According to this, the population attributable risk estimate in Germany is 3.5%.

CONCLUSION

There is sufficient evidence that smoking is associated with tinnitus. As the review mainly consists of cross-sectional studies, the observed correlation does not give evidence of a causal relationship. Due to the impact of various confounders, further research is needed to provide more evidence on the strength of association and causal relationships.

Impact of Nicotine Exposure on Hair Cell Toxicity and Embryotoxicity During Zebrafish Development

Objectives

Nicotine has various adverse effects including negative impacts associated with maternal exposure. In the current study, we examined nicotine-induced damage of hair cells and embryotoxicity during zebrafish development.

Methods

Zebrafish embryos were exposed to nicotine at several concentrations (5, 10, 20, and 40 μM) and embryotoxicity were evaluated at 72 hours, including hatching rate, mortality, teratogenicity rate, and heart rate. Hair cells within the supraorbital (SO1 and SO2), otic (O1), and occipital (OC1) neuromasts were identified at 120 hours. Apoptosis and mitochondrial damage of hair cells were analyzed using TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling) and DASPEI (2-[4-(dimethylamino)styryl]-N-ethylpyridinium iodide) assays, respectively, and changes of ultrastructure were observed by scanning electron microscopy.

Results

The control group without nicotine appeared normal with overall mortality and teratogenicity rate <5%. The hatching rate and mortality rate was not significantly different according to nicotine concentration (n=400 each). The abnormal morphology rate (n=400) increased and heart rate (n=150) decreased with increasing nicotine concentration (P<0.05). Nicotine-induced hair cell damage significantly increased as nicotine concentration increased. A significantly greater number of TUNEL-positive cells (P<0.01) and markedly smaller DASPEI area (P<0.01) were shown as nicotine concentration increased.

Conclusion

The current results suggest that nicotine induces dose-dependent hair cell toxicity in embryos by promoting apoptosis and mitochondrial and structural damage.

Increased medial olivocochlear reflex strength in normal-hearing, noise-exposed humans

Research suggests that college-aged adults are vulnerable to tinnitus and hearing loss due to exposure to traumatic levels of noise on a regular basis. Recent human studies have associated exposure to high noise exposure background (NEB, i.e., routine noise exposure) with the reduced cochlear output and impaired speech processing ability in subjects with clinically normal hearing sensitivity. While the relationship between NEB and the functions of the auditory afferent neurons are studied in the literature, little is known about the effects of NEB on functioning of the auditory efferent system. The objective of the present study was to investigate the relationship between medial olivocochlear reflex (MOCR) strength and NEB in subjects with clinically normal hearing sensitivity. It was hypothesized that subjects with high NEB would exhibit reduced afferent input to the MOCR circuit which would subsequently lead to reduced strength of the MOCR. In normal-hearing listeners, the study examined (1) the association between NEB and baseline click-evoked otoacoustic emissions (CEOAEs) and (2) the association between NEB and MOCR strength. The MOCR was measured using CEOAEs evoked by 60 dB pSPL linear clicks in a contralateral acoustic stimulation (CAS)-off and CAS-on (a broadband noise at 60 dB SPL) condition. Participants with at least 6 dB signal-to-noise ratio (SNR) in the CAS-off and CAS-on conditions were included for analysis. A normalized CEOAE inhibition index was calculated to express MOCR strength in a percentage value. NEB was estimated using a validated questionnaire. The results showed that NEB was not associated with the baseline CEOAE amplitude (r = -0.112, p = 0.586). Contrary to the hypothesis, MOCR strength was positively correlated with NEB (r = 0.557, p = 0.003). NEB remained a significant predictor of MOCR strength (β = 2.98, t(19) = 3.474, p = 0.003) after the unstandardized coefficient was adjusted to control for effects of smoking, sound level tolerance (SLT) and tinnitus. These data provide evidence that MOCR strength is associated with NEB. The functional significance of increased MOCR strength is discussed.

Sex-Related Cochlear Impairment in Cigarette Smokers

Background

A number of studies have documented the influence of cigarette smoking on hearing. However, the association between sex and hearing impairment in smokers as measured by otoacoustic emissions (OAEs) has not been clearly established. The aim of this study was to analyze sex-specific effects of smoking on hearing via conventional and ultra-high-frequency pure tone audiometry (PTA), and OAEs, specifically spontaneous OAEs, click-evoked OAEs, and distortion-product OAEs.

Material/Methods

The study included 84 healthy volunteers aged 25–45 years (mean 34), among them 46 women (25 non-smokers and 21 smokers) and 38 men (16 non-smokers and 22 smokers). The protocol of the study included otoscopic examination, tympanometry, low-, moderate-, and ultra-high-frequency PTA, evaluation of spontaneous click-evoked (CEAOEs) and distortion-product otoacoustic emissions (DPOAEs), assessment of the DP-grams for 2f₁-f₂ (f₁ from 977 to5 164 Hz), and input/output function at L₂ primary tone level of 40–70 dB SPL.

Results

Smokers and non-smokers did not differ significantly in terms of their hearing thresholds assessed with tone audiometry. Male smokers presented with significantly lower levels of CEAOEs and DPOAEs than both male non-smokers and female smokers.

Conclusions

Smoking does not modulate a hearing threshold determined with PTA at low, moderate, and ultra-high frequencies, but causes a significant decrease in OAE levels. This effect was observed only in males, which implies that they are more susceptible to smoking-induced hearing impairment. Sex-specific differences in otoacoustic emissions level may reflect influences of genetic, hormonal, behavioral, and/or environmental factors.

Influência de fatores e hábitos pessoais na percepção do zumbido

RESUMO Objetivo: investigar a localização e verificar a influência de fatores e hábitos na percepção do zumbido em pacientes com tal sintoma. Métodos: fizeram parte da amostra 740 indivíduos com queixa de zumbido, atendidos em ambulatório especializado de hospital universitário. Todos relataram a localização do zumbido em resposta a questionário, contendo também informações sobre fatores e hábitos causadores de melhora ou piora na percepção do zumbido. Os dados foram analisados estatisticamente. Resultados: o predomínio da localização foi em ambas as orelhas. A maior parte dos fatores investigados não modifica a percepção do zumbido para os pesquisados. Dentre os fatores que puderam ser relacionados à piora da percepção estão, principalmente, o silêncio e o período da noite, seguidos pela ansiedade. Por outro lado, ruído foi o fator mais referido como causador de diminuição da percepção do zumbido. Não foi verificada influência de idade e gênero. Conclusão: mais da metade dos sujeitos apresentaram queixa de zumbido bilateral e a maior parte das situações pesquisadas não provocam mudança na percepção do zumbido na população estudada. Destaca-se, contudo, que a presença de ruído ambiental auxilia na diminuição da sensação de incômodo ao zumbido, enquanto o silêncio, período da noite e a ansiedade contribuem para acentuá-la.

Otoacoustic Emissions in Smoking and Nonsmoking Young Adults

Objectives

The present study investigates the usefulness of transiently evoked otoacoustic emissions (TEOAEs) and distortion product OAEs (DPOAEs) in detecting small changes in the hearing of young smoking adults.

Methods

Otoacoustic emissions were acquired from the ears of 48 young adults (age, 20 to 27 years). The dataset was divided into two groups, smoking (24 persons/48 ears) and nonsmoking (24 persons/48 ears). The level of smoking was relatively small in comparison to previous studies, an average of 3.8 years and 8.7 cigarettes per day. In each ear three OAE measurements were made: TEOAEs, DPOAEs, and spontaneous OAEs (SOAEs). Pure tone audiometry and tympanometry were also conducted. Audiometric thresholds did not differ significantly between the datasets. Half-octave-band values of OAE signal to noise ratios and response levels were used to assess statistical differences.

Results

Averaged data initially revealed that differences between the two study groups occurred only for TEOAEs at 1 kHz. However when the datasets were divided into ears with and without SOAEs more differences became apparent, both for TEOAEs and DPOAEs. In ears that exhibited SOAEs, both smokers and nonsmokers, there were no statistically significant differences between evoked OAEs; however in all ears without SOAEs, evoked OAEs were higher in the ears of nonsmokers, by as much as 5 dB. These differences were most prominent in the 1-2 kHz range.

Conclusion

A general decrease in OAE levels was found in the group of smokers. However, in ears which exhibited SOAEs, there was no difference between the evoked OAEs of smokers and nonsmokers. We conclude that smoking had not yet measurably affected the ears of those with acute hearing (i.e., those who exhibit SOAEs). However, in ears without SOAEs, smokers exhibited smaller evoked OAE amplitudes than nonsmokers, even though their audiometric thresholds were within the norm.

Simultaneous effects of noise exposure and smoking on OAEs

Noise is one of the most pervasive hazardous factors in the workplace. Noise-induced hearing loss (NIHL) is the most common disorder related to noise exposure. Smoking is probably associated with hearing loss. The simultaneous effect of noise and smoking on hearing is a recent concern. In this study, we assessed the simultaneous effect of noise and smoking on standard pure tone audiometry (PTA) and distortion product otoacoustic emissions (DP-OAEs). This was an historical cohort study on 224 workers exposed to noise who were divided into two groups: Smokers and nonsmokers. DP-OAE response amplitudes were assessed. Data were analyzed by SPSS software (version 19) using Student's t-test and Mann-Whitney U test. One hundred and five subjects were smokers (case group) and 119 individuals were nonsmokers (control group). All the subjects were exposed to 91.08 + 2.29 dBA [time-weighted average (TWA) for an 8 h work shift]. Mean DP-OAE response amplitude at frequencies higher than 1,000 Hz was significantly higher in the smokers than the nonsmokers. This study showed that smoking can aggravate the effect of noise on hearing in DP-OAEs.

Concurrent effect of noise exposure and smoking on extended high-frequency pure-tone thresholds

OBJECTIVE

Concurrent effect of noise and smoking on hearing loss is a recent concern. In this study, the concurrent effect of noise and smoking on hearing loss in conventional frequencies and frequencies higher than 8 kHz was assessed.

DESIGN

This was a cross-sectional study on workers exposed to noise who were divided into two groups: smokers and non-smokers. Hearing thresholds were assessed by conventional audiometry, and HFA. Data were analysed using non-parametric tests and Student's t-test.

STUDY SAMPLE

There were 212 workers.

RESULTS

Ninety-seven subjects were smokers and 115 individuals were non-smokers. All subjects were exposed to 92.1 ± 2.4 dBA (Leq8h). The highest threshold in conventional and high-frequency audiometry was observed at 6 kHz and 16 kHz, respectively. Hearing threshold at frequencies above 1 kHz was significantly higher in the smokers than non-smokers. There was no correlation between hearing thresholds and pack-years of smoking.

CONCLUSIONS

Concurrent exposure to noise and smoking may be associated with more hearing loss than exposure to noise alone in the conventional and high frequencies. However, other differences between smokers and non-smokers may explain these differences as well.

Effect of nicotine on the structure of cochlea of guinea pigs

Smoking has been positively associated with hearing loss in human. However, its effect on the cochlea has not been previously evaluated. Aim of work is to investigate the effect of nicotine, which is the primary pharmacological component of tobacco, on the structure of the cochlea of adult male guinea pigs. Fifteen male guinea pigs were classified into two groups: group I (control) and group II (nicotine treated group). Group II was further subdivided into two subgroups; IIA and IIB according to the dose of nicotine (3 mg/kg and 6 mg/kg, respectively). The cochlea was harvested and processed for light microscopy, transmission electron microscopy and scanning electron microscopy. Nicotine administration induced damage of outer hair cells which were distorted in shape with vacuolated cytoplasm and heterochromatic nuclei. Topography revealed damage of the stereocilia which included disorganization, bent and limp or complete loss and expansion of the surrounding supporting cells. These changes were more pronounced in the basal turn of the cochlea and mainly involved the outer hair cells. High dose induced more damage and resulted in protrusion of the apical poles of hair cells (blebing), particularly the outer two rows. Nicotine is proved to be harmful to the cells of the cochlea, particularly the outer hair cells of the basal turn. High doses induce blebing of hair cells.

Limiares auditivos tonais, emissões otoacústicas e sistema olivococlear medial de ex-usuários de drogas

Objetivos analisar se o uso de drogas ilícitas pode interferir nos sistemas auditivos periférico e central. Métodos a amostra foi composta por 17 indivíduos distribuídos conforme o tipo de droga mais consumida: 10 indivíduos no grupo maconha (G1) e sete no grupo crack/cocaína (G2). Os grupos foram subdivididos segundo o tempo de uso de drogas: um a cinco, seis a 10 e mais que 15 anos. Foram avaliados por meio de anamnese, audiometria tonal liminar, imitânciometria, emissões otoacústicas transientes (EOAT) e efeito supressor das EOAT. Resultados comparando os limiares tonais do G1 e G2, observaram-se limiares elevados para o G2, com diferença estatisticamente significante no grupo de um a cinco anos para 250, 500, 6000 e 8000Hz na orelha direita e de seis a 10 anos para 4000 e 8000Hz na orelha esquerda. Para usuários por mais que 15 anos, observou-se limiares superiores a 25dBNA de 3000 a 8000Hz na orelha direita. Nas EOAT e efeito supressor das EOAT não houve diferença estatisticamente significante entre G1 e G2 e entre os tempos de uso das drogas. O G1 apresentou relação sinal/ruído das EOAT superior ao G2. O efeito supressor das EOAT esteve presente em 79% das orelhas avaliadas. Conclusão na amostra estudada, o crack/cocaína apresentou efeito mais deletério sobre o sistema auditivo do que a maconha. O maior tempo de uso de drogas influenciou nos resultados do G1. O uso de drogas ilícitas não provocou alterações no SOCM.

Cochlear efferent innervation and function

PURPOSE OF REVIEW

This review covers topics relevant to olivocochlear-efferent anatomy and function for which there are new findings in papers from 2009 to early 2010.

RECENT FINDINGS

Work within the review period has increased our understanding of medial olivocochlear (MOC) mechanisms in outer hair cells, MOC-reflex tuning, MOC effects on distortion product otoacoustic emissions, the time course of MOC effects, MOC effects in psychophysical tests and on understanding speech, MOC effects in attention and learning, and lateral efferent function in binaural hearing. In addition, there are new insights into efferent molecular mechanisms and their effect on cochlear development.

SUMMARY

Techniques for measuring efferent effects using otoacoustic emissions are now well developed and have promise in clinical applications ranging from predicting which patients are susceptible to acoustic trauma to characterizing relationships between efferent activation and learning disabilities. To realize this promise, studies are needed in which these techniques are applied with high standards.