Impacts of hazardous noise levels on hearing loss and tinnitus in dental professionals

Fredriksson S., Li H., Söderberg M., Gyllensten K., Widén S., Persson Waye K.

Togoo R.A., Alhaider S.H., Hakami R.M., Alzamil N.S., Alassmi A.A., AlShahrani A.A., Moadi R.A., Ain T.S.

Natarajan N., Batts S., Stankovic K.M.

Noise-induced hearing loss (NIHL) is the second most common cause of sensorineural hearing loss, after age-related hearing loss, and affects approximately 5% of the world’s population. NIHL is associated with substantial physical, mental, social, and economic impacts at the patient and societal levels. Stress and social isolation in patients’ workplace and personal lives contribute to quality-of-life decrements which may often go undetected. The pathophysiology of NIHL is multifactorial and complex, encompassing genetic and environmental factors with substantial occupational contributions. The diagnosis and screening of NIHL are conducted by reviewing a patient’s history of noise exposure, audiograms, speech-in-noise test results, and measurements of distortion product otoacoustic emissions and auditory brainstem response. Essential aspects of decreasing the burden of NIHL are prevention and early detection, such as implementation of educational and screening programs in routine primary care and specialty clinics. Additionally, current research on the pharmacological treatment of NIHL includes anti-inflammatory, antioxidant, anti-excitatory, and anti-apoptotic agents. Although there have been substantial advances in understanding the pathophysiology of NIHL, there remain low levels of evidence for effective pharmacotherapeutic interventions. Future directions should include personalized prevention and targeted treatment strategies based on a holistic view of an individual’s occupation, genetics, and pathology.

Vasudevamurthy S., Kumar U. A.

Objectives: Adverse effects of noise exposure on hearing and cognition are well documented in the literature. Recently, it has becoming increasingly evident that noise exposure deteriorates suprathreshold auditory skills, even though the hearing sensitivity is intact. This condition is termed as cochlear synaptopathy or hidden hearing loss, which is apparent in animal models. However, equivocal findings are reported in humans. This study aimed at assessing the working memory, attention abilities, and suprathreshold hearing abilities in normal-hearing individuals with and without occupational noise exposure. We also explored the relationship between cognitive measures and suprathreshold auditory measures. Design: The study participants were divided into two groups. All the participants had normal-hearing thresholds. The control group consisted of 25 individuals with no occupational noise exposure, whereas the noise exposure group had 25 individuals exposed to occupational noise of 85 dBA for a minimum period of 1 year. Working memory was assessed using auditory digit span (forward and backward), operation span, and reading span. The Erikson flanker test was used to evaluate attention abilities. The suprathreshold hearing was assessed in terms of gap detection thresholds and sentence identification in noise. Results: The results showed that the noise exposure group performed poorly compared to the control group on all auditory and cognitive tasks except the reading span. Conclusion: The results of the study suggest that occupational noise exposure may hamper the cognitive skills and suprathreshold hearing abilities of the individual despite having normal peripheral hearing.

Wang Q., Wang X., Yang L., Han K., Huang Z., Wu H.

Significant sex differences exist in hearing physiology, while few human studies have investigated sex differences in noise-induced hearing loss (NIHL), and the sex bias in previous studies resulted in inadequate female data. The study aims to investigate sex differences in the characteristics of NIHL to provide insight into sex-specific risk factors, prevention strategies and treatment for NIHL. This cross-sectional study included 2280 industrial noise-exposed shipyard workers (1140 males and 1140 females matched for age, job and employment length) in China. Individual noise exposure levels were measured to calculate the cumulative noise exposure (CNE), and an audiometric test was performed by an experienced technician in a soundproof booth. Sex differences in and influencing factors of low-frequency (LFHL) and high-frequency hearing loss (HFHL) were analyzed using logistic regression models stratified by age and CNE. At comparable noise exposure levels and ages, the prevalence of HFHL was significantly higher in males (34.4%) than in females (13.8%), and males had a higher prevalence of HFHL (OR = 4.19, 95% CI 3.18 to 5.52) after adjusting for age, CNE, and other covariates. Sex differences were constant and highly remarkable among subjects aged 30 to 40 years and those with a CNE of 80 to 95 dB(A). Alcohol consumption might be a risk factor for HFHL in females (OR = 3.12, 95% CI 1.10 to 8.89). This study indicates significant sex differences in NIHL. Males are at higher risk of HFHL than females despite equivalent noise exposure and age. The risk factors for NIHL might be different in males and females.

Li X., Dong Q., Wang B., Song H., Wang S., Zhu B.

This study was conducted to estimate the current prevalence of hypertension, cardiovascular condition and hearing difficulty of workers exposure to occupational noise, and to analyze any associations between these abnormal signs and occupational noise exposure. The subjects included 5205 noise-exposed workers. Workers with high noise exposure were more likely to have a higher threshold value than low exposure ones (P < 0.05). Subjects in the high exposure group had a significantly higher risk of hypertension and hearing loss than the ones in low exposure group. Between the ages of 30 and 45, high-level occupational noise exposure led to a significantly raising risk of both hypertension (Adjusted OR = 1.59, 95% CI, 1.19–2.11) and hearing loss (Adjusted OR = 1.28, 95% CI, 1.03–1.60) when comparing to low-level noise exposure. In male workers, the prevalence of hearing difficulty in high exposure group was approximately 1.2 times worse than in low group (P = 0.006). In addition, exposure to high noise level demonstrated a significant association with hypertension and hearing loss when the duration time to occupational noise was longer than 10 years. Hypertension and hearing difficulty is more prevalent in the noise-exposed group (higher than 85 dB[A]). Steps to reduce workplace noise levels and to improve workplace-based health are thus urgently needed.

Yang Y., Zhang E., Zhang J., Chen S., Yu G., Liu X., Peng C., Lavin M.F., Du Z., Shao H.

At present, occupational noise exposure has become one of the risk factors of occupational workers and attracted serious concerned of most of occupational disease researchers. To assess associations of occupational noise exposure and cardiovascular disease by meta-analysis.Results from primary studies about occupational noise and cardiovascular disease (2000-2017) were retrieved from literatures, which were conducted in China only. Both random and fixed effect model were used to calculate pooled odds ratio (OR) and their corresponding 95% confidence interval (CI). Review Manager and Stata software were used to perform data analysis. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statements.After applying stringent inclusion and exclusion criteria, 4771 exposures and 3068 controls from 11 primary studies were used to analyze the relationship between occupational noise exposure and cardiovascular disease. The risk of developing high blood pressure for workers exposed to noise is 2.55 times higher than the controls (I = 52%, 95% CI: 1.94-3.36), and electrocardiograph (ECG) abnormality is 2.27 times higher than the control groups (I = 22%, 95% CI: 1.96-2.62). The bias analysis suggested that there is publication bias, but it didn't affect the conclusions from trim test.The impact of high-intensity noise exposure on the worker's cardiovascular system is much greater than that of the unexposed control group, and the effect on hypertension of the exposed group is greater than that of the ECG.

Hoffman H.J., Dobie R.A., Losonczy K.G., Themann C.L., Flamme G.A.

As the US population ages, effective health care planning requires understanding the changes in prevalence of hearing loss.To determine if age- and sex-specific prevalence of adult hearing loss has changed during the past decade.We analyzed audiometric data from adults aged 20 to 69 years from the 2011-2012 cycle of the US National Health and Nutrition Examination Survey, a cross-sectional, nationally representative interview and examination survey of the civilian, noninstitutionalized population, and compared them with data from the 1999-2004 cycles. Logistic regression was used to examine unadjusted, age- and sex-adjusted, and multivariable-adjusted associations with demographic, noise exposure, and cardiovascular risk factors. Data analysis was performed from April 28 to June 3, 2016.Audiometry and questionnaires.Speech-frequency hearing impairment (HI) defined by pure-tone average of thresholds at 4 frequencies (0.5, 1, 2, and 4 kHz) greater than 25 decibels hearing level (HL), and high-frequency HI defined by pure-tone average of thresholds at 3 frequencies (3, 4, and 6 kHz) greater than 25 decibels HL.Based on 3831 participants with complete threshold measurements (1953 men and 1878 women; mean [SD] age, 43.6 [14.4] years), the 2011-2012 nationally weighted adult prevalence of unilateral and bilateral speech-frequency HI was 14.1% (27.7 million) compared with 15.9% (28.0 million) for the 1999-2004 cycles; after adjustment for age and sex, the difference was significant (odds ratio [OR], 0.70; 95% CI, 0.56-0.86). Men had nearly twice the prevalence of speech-frequency HI (18.6% [17.8 million]) as women (9.6% [9.7 million]). For individuals aged 60 to 69 years, speech-frequency HI prevalence was 39.3% (95% CI, 30.7%-48.7%). In adjusted multivariable analyses for bilateral speech-frequency HI, age was the major risk factor (60-69 years: OR, 39.5; 95% CI, 10.5-149.4); however, male sex (OR, 1.8; 95% CI, 1.1-3.0), non-Hispanic white (OR, 2.3; 95% CI, 1.3-3.9) and non-Hispanic Asian race/ethnicity (OR, 2.1; 95% CI, 1.1-4.2), lower educational level (less than high school: OR, 4.2; 95% CI, 2.1-8.5), and heavy use of firearms (≥1000 rounds fired: OR, 1.8; 95% CI, 1.1-3.0) were also significant risk factors. Additional associations for high-frequency HI were Mexican-American (OR, 2.0; 95% CI, 1.3-3.1) and other Hispanic race/ethnicity (OR, 2.4; 95% CI, 1.4-4.0) and the combination of loud and very loud noise exposure occupationally and outside of work (OR, 2.4; 95% CI, 1.4-4.2).Adult hearing loss is common and associated with age, other demographic factors (sex, race/ethnicity, and educational level), and noise exposure. Age- and sex-specific prevalence of HI continues to decline. Despite the benefit of delayed onset of HI, hearing health care needs will increase as the US population grows and ages.

Masterson E.A., Bushnell P.T., Themann C.L., Morata T.C.

Hearing loss is the third most common chronic physical condition in the United States, and is more prevalent than diabetes or cancer (1). Occupational hearing loss, primarily caused by high noise exposure, is the most common U.S. work-related illness (2). Approximately 22 million U.S. workers are exposed to hazardous occupational noise (3). CDC compared the prevalence of hearing impairment within nine U.S. industry sectors using 1,413,789 noise-exposed worker audiograms from CDC's National Institute for Occupational Safety and Health (NIOSH) Occupational Hearing Loss Surveillance Project (4). CDC estimated the prevalence at six hearing impairment levels, measured in the better ear, and the impact on quality of life expressed as annual disability-adjusted life years (DALYs), as defined by the 2013 Global Burden of Disease (GBD) Study (5). The mining sector had the highest prevalence of workers with any hearing impairment, and with moderate or worse impairment, followed by the construction and manufacturing sectors. Hearing loss prevention, and early detection and intervention to avoid additional hearing loss, are critical to preserve worker quality of life.

Lie A., Skogstad M., Johnsen T.S., Engdahl B., Tambs K.

Noise-induced hearing loss (NIHL) is one of the most reported occupational diseases internationally. The occurrence of audiometric notches is emphasized in both American and European guidelines for the diagnosis of NIHL. The aim of this study was to describe the prevalence of notched audiograms among railway personnel with and without noise exposure to better assess the usefulness of such notches in the diagnosis of NIHL.The most recent audiogram from 1994 to 2011 of a total of 12,055 railway workers, age 20 to 65 years, was obtained from the medical records of the occupational health service of the Norwegian State Railways (NSB). The prevalences of three types of notched audiograms, Coles notch, notch index, and 4 kHz notch, were computed, in relation to age, sex, and occupational noise exposure.Coles notch in either ear was found in 63% of the male railway maintenance workers, exposed to noise levels of 75 to 90 dB(A), compared with 53% of the non-noise exposed (

Basner M., Babisch W., Davis A., Brink M., Clark C., Janssen S., Stansfeld S.

Noise is pervasive in everyday life and can cause both auditory and non-auditory health effects. Noise-induced hearing loss remains highly prevalent in occupational settings, and is increasingly caused by social noise exposure (eg, through personal music players). Our understanding of molecular mechanisms involved in noise-induced hair-cell and nerve damage has substantially increased, and preventive and therapeutic drugs will probably become available within 10 years. Evidence of the non-auditory effects of environmental noise exposure on public health is growing. Observational and experimental studies have shown that noise exposure leads to annoyance, disturbs sleep and causes daytime sleepiness, affects patient outcomes and staff performance in hospitals, increases the occurrence of hypertension and cardiovascular disease, and impairs cognitive performance in schoolchildren. In this Review, we stress the importance of adequate noise prevention and mitigation strategies for public health.

Willershausen B., Callaway A., Wolf T.G., Ehlers V., Scholz L., Wolf D., Letzel S.

Extended exposure to high-speed handpieces and other noise-intensive devices might put dentists at risk for possible hearing impairment. The aim of this study was to determine the hearing ability of dentists and other scientists for comparison. After approval by the ethics committee, 115 subjects (dentists and other academic professionals as controls) of both genders were enrolled in the study. Exclusion criteria were colds, ear-blockages or abnormal hearing-thresholds. An audiometric determination (Oscilla USB audiometer, AudioConsole 3, Inmedico A/S, Denmark) was performed in the frequency range of 125Hz to 8 kHz for both ears. Anamnestic data and number of years in the profession were assessed using a questionnaire. Differences between groups were analyzed with the Mann–Whitney-U-test. Data from 53 dentists and 55 other academic professionals (69.4% male, 30.6% female) with a mean age of 51.7 ± 9.6 years and similar gender distributions in both groups were analyzed. The audiometric tests for the right and left air conduction showed that the hearing of dentists tended to be slightly more impaired than in the control subjects. For the frequencies 3 kHz and 4 kHz these differences were statistically significant for both ears. In contrast, no significant differences were found in this range for bone conduction. Hearing impairment in dentists was slightly higher than in controls. Although other factors like environmental noise exposure were comparable for both groups, occupational exposure to high-speed handpieces and other noisy devices can be an additional burden for the hearing.

Henry J.A., Roberts L.E., Caspary D.M., Theodoroff S.M., Salvi R.J.

Background: The study of tinnitus mechanisms has increased tenfold in the last decade. The common denominator for all of these studies is the goal of elucidating the underlying neural mechanisms of tinnitus with the ultimate purpose of finding a cure. While these basic science findings may not be immediately applicable to the clinician who works directly with patients to assist them in managing their reactions to tinnitus, a clear understanding of these findings is needed to develop the most effective procedures for alleviating tinnitus. Purpose: The goal of this review is to provide audiologists and other health-care professionals with a basic understanding of the neurophysiological changes in the auditory system likely to be responsible for tinnitus. Results: It is increasingly clear that tinnitus is a pathology involving neuroplastic changes in central auditory structures that take place when the brain is deprived of its normal input by pathology in the cochlea. Cochlear pathology is not always expressed in the audiogram but may be detected by more sensitive measures. Neural changes can occur at the level of synapses between inner hair cells and the auditory nerve and within multiple levels of the central auditory pathway. Long-term maintenance of tinnitus is likely a function of a complex network of structures involving central auditory and nonauditory systems. Conclusions: Patients often have expectations that a treatment exists to cure their tinnitus. They should be made aware that research is increasing to discover such a cure and that their reactions to tinnitus can be mitigated through the use of evidence-based behavioral interventions.

M Elmehdi H.

Campo P., Venet T., Rumeau C., Thomas A., Rieger B., Cour C., Cosnier F., Parietti-Winkler C.

Presbycusis, or age-related hearing loss is a growing problem as the general population ages. In this longitudinal study, the influence of noise or styrene exposure on presbycusis was investigated in Brown Norway rats. Animals were exposed at 6 months of age, either to a band noise centered at 8 kHz at a Lex,8h = 85 dB (86.2 dB SPL for 6 h), or to 300 ppm of styrene for 6 h per day, five days per week, for four weeks. Cubic distortion product otoacoustic emissions (2f1-f2 DPOAEs) were used to test the capacity of the auditory receptor over the lifespan of the animals. 2f1-f2DPOAE measurements are easy to implement and efficiently track the age-related deterioration of mid- and high-frequencies. They are good indicators of temporary auditory threshold shift, especially with a level of primaries close to 60 dB SPL. Post-exposure hearing defects are best identified using moderate, rather than high, levels of primaries. Like many aging humans, aging rats lose sensitivity to high-frequencies faster than to medium-frequencies. Although the results obtained with the styrene exposure were not entirely conclusive, histopathological data showed the presbycusis process to be enhanced. Noise-exposed rats exhibit a loss of spiral ganglion cells from 12 months and a 7 dB drop in 2f1-f2DPOAEs at 24 months, indicating that even moderate-intensity noise can accelerate the presbycusis process. Even though the results obtained with the styrene exposure are less conclusive, the histopathological data show an enhancement of the presbycusis process.