Noise Exposure and Hearing Impairment in Air Force Pilots.

OBJECTIVE: The goal of this study was to estimate noise exposure and hearing impairments in Swedish military pilots. It also aimed to analyze possible relations between noise exposure and hearing impairments.METHODS: The study group was an open cohort of 337 male pilots. They were longitudinally followed with pure tone audiograms every fifth year from the beginning of flight service until discharge. Outcome measures were prevalence of thresholds >20 dB HL and >40 dB HL at different ages, and incidence of impairments >20 dB HL, 30 dB HL, and 40 dB HL. Exposure variables were individual flight data and noise dose measurements. The ISO 1999 Database A was used for reference data.RESULTS: At 50 yr of age, 41% of the pilots were exposed to an equivalent noise dose exceeding the EU action level of Leq 80 dB(A). We observed significant elevated prevalence values of thresholds >20 dB HL in all age classes compared to the ISO 1999 Database A. These elevations were most pronounced at ages 30 and 40 yr and at 4 and 6 kHz in the left ear. Significantly elevated prevalence values of thresholds >40 dB HL compared to the ISO 1999 Database A were observed at age 40 and 50 yr at 4 and 6 kHz. In a Cox analysis we observed elevated hazard ratios of deteriorating thresholds with longer flight time/year in fast jet pilots.DISCUSSION: Military pilots had elevated prevalence values of hearing impairment. Of the subjects, 41% had been exposed to noise exceeding the EU risk limit. Increased flight time/year and flying fast jets were associated with elevated risk of hearing deterioration.Muhr P, Johnson A-C, Selander J, Svensson E, Rosenhall U. Noise exposure and hearing impairment in air force pilots. Aerosp Med Hum Perform. 2019; 90(9):757-763.

Severe-to-profound hearing impairment: demographic data, gender differences and benefits of audiological rehabilitation.

Purpose: The purpose of this study was to identify and report demographic data of patients with severe-to-profound hearing loss, assess participation in audiological rehabilitation and analyze the benefits of various rehabilitation methods.Materials and methods: Data on 4286 patients with severe-to-profound hearing impairments registered in the Swedish Quality Register of Otorhinolaryngology over a period from 2006-2015 were studied. Demographic data, gender differences, audiological rehabilitation and benefits of the rehabilitation were analyzed.Results: Group rehabilitation and visits to a hearing rehabilitation educator provided the most benefits in audiological rehabilitation. Only 40.5% of the patients received extended audiological rehabilitation, of which 54.5% were women. A total of 9.5% of patients participated in group rehabilitation, with 59.5% being women. Women also visited technicians, welfare officers, hearing rehabilitation educators, psychologists and physicians and received communication rehabilitation in a group and fit with cochlea implants significantly more often than did men.Conclusions: The study emphasizes the importance of being given the opportunity to participate in group rehabilitation and meet a hearing rehabilitation educator to experience the benefits of hearing rehabilitation. There is a need to offer extended audiological rehabilitation, especially in terms of gender differences, to provide the same impact for women and men.Implications for RehabilitationSignificantly more women than men with severe-to-profound hearing impairment receive audiological rehabilitation.Hearing impairment appears to have a significantly more negative impact on women's quality of life than men's.It is important to offer extended audiological rehabilitation to all patients with severe-to-profound hearing loss to obtain an equal hearing health care regardless of gender.

Declining and fluctuating prevalence values of hearing impairment in 18-year old Swedish men during three decades.

OBJECTIVE: To analyze time trends in prevalence of hearing impairment in almost complete birth cohorts of 18-year old Swedish men from 1970s up to 2010. STUDY GROUPS: Before 1999, all 18-year old men, in Sweden, were called for a compulsory conscription examination. In 1971-1999, the participation rate in audiometry was 73-95%. After 1999, when exemption from conscription was allowed, the participation rate gradually declined to 52% in 2004. Samples with participation rates below 50% (2005-2010) were considered non-representative and excluded from the analyses. RESULTS: High-frequency hearing impairments (HFHI) 35-40 dB HL and ≥45 dB HL showed a decreasing trend over the observed period, from a prevalence of 2.9% (35-40 dB HL) and 3.8% (≥45 dB HL) respectively in 1971 to 1.4% and 1.1% respectively in 2004. HFHI 25-30 dB HL, showed slow variations over time and decreased from 8.5% in 1971 to 3.2% in 1981 followed by an increase to 10.4% in 1992. After that year there was a decrease to 5.2% in 2004. The slow fluctuations affected only HFHI 25-30 dB HL, mainly at 6 kHz. The left ear was more affected than the right ear. CONCLUSIONS: The most important observation was a decrease of HFHI 35-40 dB HL by 52% percent and of HFHI ≥45 dB HL by 71% between the years 1971 and 2004. The prevalence of HFHI 25-30 dB HL in young Swedish males fluctuated over a period of 33 years. Possible reasons for these trends and variations are discussed.

Influence of well-known risk factors for hearing loss in a longitudinal twin study.

OBJECTIVE: The aim was to investigate the influence of environmental exposures on hearing loss in a twin cohort. STUDY SAMPLE: Male twins born 1914-1958, representing an unscreened population, were tested for hearing loss at two occasions, 18 years apart. DESIGN: Clinical audiometry and a questionnaire were performed at both time points in this longitudinal study. Noise and solvent exposure were assessed using occupational work codes and a job exposure matrix. Hearing impairment was investigated using two different pure tone averages: PTA4 (0.5, 1, 2, and 4 kHz) and HPTA4 (3, 4, 6, and 8 kHz). RESULTS: Age affected all outcome measures. Noise exposure between time point one and two affected the threshold shifts of PTA4 and HPTA4 more in participants with a pre-existing hearing loss at time point one. Lifetime occupational noise exposure was a risk factor especially for the low-frequency hearing threshold PTA4. Firearm use was a statistically significant risk factor for all outcome measures. CONCLUSIONS: Pre-existing hearing loss can increase the risk of hearing impairment due to occupational noise exposure. An increased risk for NIHL was also seen in the group with exposures below 85 dB(A), a result that indicates awareness of NIHL should be raised even for those working in environments where sound levels are below 85 dB(A).

A demonstrated positive effect of a hearing conservation program in the Swedish armed forces.

OBJECTIVE: A revised hearing conservation program (HCP) was implemented in the Swedish Armed Forces in 2002. The aim of this study was to evaluate the incidence of significant threshold shifts (STS) in male conscripts heavily exposed to noise after the implementation of the new HCP, comparing the results to those of an earlier study from 1999/2000. DESIGN: The study was prospective and longitudinal, covering the period from reporting to military service to discharge. The outcome measure was the incidence of STS. Statistics from the military insurance system was analysed. STUDY SAMPLE: A total of 395 conscripts were included in the study (mean age 19 years). The control group (n: 839) consisted of men of the same age. RESULTS: In 2004/2005 the incidence rate of STS was 2.3% compared to 7.9% in 1999/2000 and compared to 3.7% among the controls. The number of cases of auditory complications reported from conscripts to the insurance system has decreased, from 16 to 5/100,000 days of military training, during the last decade. CONCLUSIONS: The new HCP apparently reduced the incidence rate of STS to one third compared to before the program was introduced and leveled it to the incidence rate in the control-group not exposed to military noise.

Subjective and clinically assessed hearing loss; a cross-sectional register-based study on a swedish population aged 18 through 50 years.

OBJECTIVES: Questionnaire studies suggest that hearing is declining among young adults. However, few studies have examined the reliability of hearing questionnaires among young adult subjects. This study examined the associations between pure tone audiometrically assessed (PTA) hearing loss and questionnaire responses in young to middle aged adults. MATERIALS AND METHODS: A cross-sectional study using questionnaire and screening PTA (500 through 6000 Hz) data from 15322 Swedish subjects (62% women) aged 18 through 50 years. PTA hearing loss was defined as a hearing threshold above 20 dB in both ears at one or more frequencies. Data were analysed with chi-square tests, nonlinear regression, binary logistic regression, and the generalized estimating equation (GEE) approach. RESULTS: The prevalence of PTA hearing loss was 6.0% in men and 2.9% in women (p < 0.001). Slight hearing impairment was reported by 18.5% of the men and 14.8% of the women (p < 0.001), whereas 0.5% of men and women reported very impaired hearing. Using multivariate GEE modelling, the odds ratio of PTA hearing loss was 30.4 (95% CI, 12.7-72.9) in men and 36.5 (17.2-77.3) in women reporting very impaired hearing. The corresponding figures in those reporting slightly impaired hearing were 7.06 (5.25-9.49) in men and 8.99 (6.38-12.7) in women. These values depended on the sound stimulus frequency (p = 0.001). The area under the ROC curve was 0.904 (0.892-0.915) in men and 0.886 (0.872-0.900) in women. CONCLUSIONS: Subjective hearing impairment predicted clinically assessed hearing loss, suggesting that there is cause for concern as regards the future development of hearing in young to middle-aged people.

The role of genetic factors for hearing deterioration across 20 years: a twin study.

BACKGROUND: Hearing deterioration at advanced ages is associated with environmental exposures (eg, to noise and solvents) and genetic influences may also be important. Little is known about the role of genetic influences on hearing when evaluated longitudinally. We sought to investigate longitudinal hearing loss in a cohort of adult male twins to evaluate the importance of genetic and environmental factors for hearing deterioration over time. METHODS: Hearing using conventional clinical audiometry was assessed in 583 male twins (128 monozygotic twin pairs and 111 dizygotic twin pairs) aged 34-79 at baseline and again two decades later. The hearing thresholds at two time points were compared at each frequency and in two different frequency regions. Genetic analyses were based on structural equation models. Bivariate Cholesky decomposition was used for longitudinal analysis. RESULTS: The prevalence of hearing loss increased over time in better and worse ear. The hearing threshold shift was more pronounced in the high-frequency region, especially at 8000 Hz. Genetic influences were moderate (heritability: 53%-65%) for pure-tone averages at both lower and higher frequencies, and were of equal magnitude at baseline and follow-up. In contrast, environmental influences were of substantial importance (55%-88%) for rate of change of the hearing threshold over the 18-year period. CONCLUSIONS: Genetic factors are of considerable importance for level of hearing acuity, but environmental factors are more important for rate of change over an 18-year period.

A multicenter study on the audiometric findings of styrene-exposed workers.

OBJECTIVE: The objective of this study was to evaluate hearing loss among workers exposed to styrene, alone or with noise. DESIGN: This cross-sectional study was conducted as part of NoiseChem, a European Commission 5th Framework Programme research project, by occupational health institutes in Finland, Sweden, and Poland. STUDY SAMPLE: Participants' ages ranged from 18-72 years (n = 1620 workers). Participants exposed to styrene, alone or with noise, were from reinforced fiberglass products manufacturing plants (n = 862). Comparison groups were comprised of workers noise-exposed (n = 400) or controls (n = 358). Current styrene exposures ranged from 0 to 309 mg/m(3), while mean current noise levels ranged from 70-84 dB(A). Hearing thresholds of styrene-exposed participants were compared with Annexes A and B from ANSI S3.44, 1996. RESULTS: The audiometric thresholds of styrene exposed workers were significantly poorer than those in published standards. Age, gender, and styrene exposure met the significance level criterion in the multiple logistic regression for the binary outcome 'hearing loss' (P = 0.0000). Exposure to noise (<85 dBA p = 0.0001; ≥85 dB(A) p = 0.0192) interacted significantly with styrene exposure. CONCLUSIONS: Occupational exposure to styrene is a risk factor for hearing loss, and styrene-exposed workers should be included in hearing loss prevention programs.

Ototoxicity of organic solvents - from scientific evidence to health policy.

The scientific workshop, organized under the 6th European Framework Programme, the Marie Curie Host Fellowship for the Transfer of Knowledge "NoiseHear" Project, by the Nofer Institute of Occupational Medicine (Lódz, Poland, 15-16 November 2006), gathered world specialists in noise, chemicals, and ototoxicity, including hearing researchers, toxicologists, otolaryngologists, audiologists and occupational health physicians.The workshop examined the evidence and the links between isolated exposure to organic solvents, combined exposure to noise and solvents, and effects on the auditory system. Its main purpose was to review the key scientific evidence to gather the necessary knowledge for developing adequate occupational health policies. This paper summarizes the workshop sessions and subsequent discussions.

Relationship between styrene exposure and hearing loss: review of human studies.

Styrene is an aromatic solvent belonging to the alkylbenzene family. Occupational exposure to styrene occurs mainly in the manufacturing of fiberglass-reinforced polyester products, e.g. reinforced plastics and composites. Since 1988, nine studies have been published on the relationship between occupational exposure to styrene and hearing loss. All studies were the cross-sectional epidemiological studies or clinical studies from occupational health clinics. A total of more than 1000 workers exposed to styrene, both with and without concurrent noise exposure, were examined using different outcome measures for hearing loss. Exposure assessment was usually based on styrene measurements in the breathing zone during several hours of one working day. Some of the studies employed also the biological monitoring of styrene exposure based on determination of its urinary metabolites. The current exposures to styrene varied between 2 and 35 ppm. In some studies, lifetime exposure was calculated using company records and questionnaire data. The current exposure to noise was estimated by noise dosimetry or standard noise measurements. Lifetime noise exposure was assessed using questionnaire data and occupational noise estimates. In many studies, noise-exposed groups were used as controls together with the unexposed workers. Of the nine studies, seven show some effects on the auditory system that were associated with styrene-alone exposure. These effects are examined using different outcome measures such as pure tone audiometry, high frequency hearing loss, and central hearing tests. In some studies, an increased risk for hearing loss was associated with exposure estimates.

Audiological findings in workers exposed to styrene alone or in concert with noise.

Audiological testing, interviews and exposure measurements were used to collect data on the health effects of styrene exposures in 313 workers from fiberglass and metal-product manufacturing plants and a mail terminal. The audiological test battery included pure-tone audiometry, distortion product otoacoustic emissions (DPOAE), psychoacoustic modulation transfer function, interrupted speech, speech recognition in noise and cortical response audiometry (CRA). Workers exposed to noise and styrene had significantly poorer pure-tone thresholds in the high-frequency range (3 to 8 kHz) than the controls, noise-exposed workers and those listed in a Swedish age-specific database. Even though abnormalities were noted on DPOAE and CRA testing, the interrupted speech and speech recognition in noise tests were the more sensitive tests for styrene effects. Further research is needed on the underlying mechanisms to understand the effects of styrene and on audiological test batteries to detect changes in populations exposed to solvents.

A guinea pig strain with recessive heredity of deafness, producing normal-hearing heterozygotes with resistance to noise trauma.

A new strain of waltzing guinea pigs arose spontaneously in a guinea pig breeding facility in Germany in 1996. In addition to obvious vestibular dysfunction, the waltzing animals appear deaf already at birth. Histological analysis revealed that the waltzers lack an open scala media due to the collapse of Reissner's membrane onto the surface of the hearing organ. Subsequent breeding has shown that this strain has a recessive mode of inheritance. The homozygotes are deaf and display a waltzing behaviour throughout their lives while the heterozygotes show no significant signs of inner ear injury despite being carriers of this specific mutated gene of hearing impairment. However, the heterozygous animals offer the opportunity to study how hereditary factors interact with auditory stress. In the present study, the susceptibility of the carriers to noise was investigated. Auditory brainstem responses were obtained prior to and after noise exposure (4 kHz, 110 dB, 6 h). The carriers were significantly less affected by the noise as compared to control animals. This difference was still significant at 4 weeks following noise exposure. It is suggested that the heterozygous animals have an endogenous resistance to auditory stress.

Low-level styrene exposure and color vision in Swedish styrene workers.

Styrene exposure and color vision for 108 workers (21-65 years) was studied at Swedish reinforced plastic plants. Acute exposure was measured at work. Data on past exposures and personal background data were collected by questionnaire. Current exposure varied between 0.3 and 96mg/m(3). Cumulative past exposures varied from 18 to 4455mg years/m(3), and an index of lifetime weighted average exposure (LWAE) varied from 5 to 129mg/m(3). Color vision was tested using the Lanthony D15 desaturated panel binocularly without prior training in conditions with ample light (1400lx). Color vision was slightly correlated to LWAE (r=0.188, p=0.052). Workers were divided into two exposure groups according to LWAE. Analyses of variance revealed effects on the Vingrys' color vision confusion index (F=6.04; p=0.016) and total error (F=6.296; p=0.014). This study thus indicates that styrene exposure even at levels below the current Swedish OEL of 20mg/m(3) may affect color vision negatively.

Beliefs and attitudes among Swedish workers regarding the risk of hearing loss.

The beliefs and attitudes regarding the risk of hearing loss and their impact on hearing protector use were investigated among Swedish workers. A questionnaire, developed by the US National Institute for Occupational Safety and Health (NIOSH), was used. The study objective was to assess workers' attitudes towards using hearing protection devices (HPDs) and to enhance the ability of workers to protect themselves from occupational hearing loss. Ninety-five per cent of the respondents were aware that loud noise could damage their hearing, 90% considered that a hearing loss would be a serious problem, and 85% believed that HPDs could protect their hearing. However, lower percentages of workers always used the HPDs when they were noise-exposed. Fifty-five per cent of the workers indicated that they could not hear warning signals when using HPDs, and 45% of the workers indicated that they considered HPDs to be uncomfortable. These issues must be addressed to make HPD use more effective.

Audiometric findings in workers exposed to low levels of styrene and noise.

Audiometry and exposure measurements were conducted on workers from fiberglass and metal products manufacturing plants and a mail distribution terminal (N = 313). Workers exposed to noise and styrene had significantly worse pure-tone thresholds at 2, 3, 4, and 6 kHz when compared with noise-exposed or nonexposed workers. Age, noise exposure, and urinary mandelic acid (a biologic marker for styrene) were the variables that met the significance level criterion in the multiple logistic regression. The odds ratios for hearing loss were 1.19 for each increment of 1 year of age (95% confidence interval [CI], 1.11-1.28), 1.18 for every decibel >85 dB(A) of noise exposure (95% CI, 1.01-1.34), and 2.44 for each millimole of mandelic acid per gram of creatinine in urine (95% CI, 1.01-5.89). Our findings suggest that exposure to styrene even below recommended values had a toxic effect on the auditory system.

NoiseChem: an European Commission research project on the effects of exposure to noise and industrial chemicals on hearing and balance.

Exposure to multiple physical and chemical agents is common in occupational environments but workplace hazards and occupational safety criteria for combined exposures are lacking. NoiseChem is an European Commission research project examining the effects of exposure to noise and chemicals on hearing and balance. Partners in Sweden, Finland, France, Denmark, UK and Poland with expert guidance from partners in the USA will examine workers and study the mechanisms of action in animals to determine the levels of risk associated with joint exposure to noise and solvents. This paper briefly outlines the project details.

NoiseChem: An European Commission research project on the effects of exposure to noise and industrial chemicals on hearing and balance.

Exposure to multiple physical and chemical agents is common in occupational environments but workplace hazards and occupational safety criteria for combined exposures is lacking. NoiseChem is an European Commission research project examining the effects of exposure to noise and chemicals on hearing and balance. Partners in Sweden, Finland, France, Denmark, UK and Poland with expert guidance from partners in USA will examine workers and study the mechanisms of action in animals to determine the levels of risk associated with joint exposure to noise and solvents. This paper briefly outlines the project details.