Hearing-aid use and its determinants in the UK National Health Service: a cross-sectional study at the Royal Surrey County Hospital.

OBJECTIVES: The aim of this study was to investigate the rate of and factors contributing to non-adherence to hearing-aid use in the UK National Health Service. DESIGN: A cross-sectional postal questionnaire survey. STUDY SAMPLE: A questionnaire, including the International Outcome Inventory for Hearing Aids, was sent to all patients fitted with hearing aids at the Royal Surrey County Hospital between 2011 and 2012 (N = 1874). A total of 1023 questionnaires were completed and returned (response rate of 55%). RESULTS: A total of 29% of responders did not use their hearing aids on a regular basis (i.e. used them less than four hours per day). Non-regular use was more prevalent in new (40%) than in existing patients (11%). Factors that reduced the risk of non-regular use included bilateral versus unilateral amplification, and moderate or severe hearing loss in the better ear. 16% of responders fitted with bilateral amplification used only one of their hearing aids. CONCLUSIONS: The level of non-regular use of hearing aids in NHS found in this study was comparable to those for other countries. Additional support might be needed for patients at a higher risk of non-regular use.

Insights from the First International Conference on Hyperacusis: causes, evaluation, diagnosis and treatment.

The First International Conference on Hyperacusis gathered over 100 scientists and health care professionals in London, UK. Key conclusions from the conference included: (1) Hyperacusis is characterized by reduced tolerance of sound that has perceptual, psychological and social dimensions; (2) there is a growing awareness that children as well as adults experience symptoms of hyperacusis or misophonia; (3) the exact mechanisms that give rise to hyperacusis are not clear, but the available evidence suggests that functional changes within the central nervous system are important and in particular, hyperacusis may be related to increased gain in the central auditory pathways and to increased anxiety or emotional response to sound; (4) various counseling and sound therapy approaches seem beneficial in the management of hyperacusis, but the evidence base for these remains poor.

The accuracy of matching target insertion gains with open-fit hearing aids.

PURPOSE: To assess the accuracy with which target insertion gains were matched for a single type of open-fit hearing aid, both on initial fitting and after adjustment. METHOD: The hearing aids were fitted using the first-fit setting in the programming software and the target formula was selected as NAL-NL1. The difference between the real ear insertion gain (REIG) and the NAL-NL1 target REIG was recorded. The initial fitting was considered acceptable if the difference was less than 10 dB at all frequencies. If an initial fitting was not acceptable, the frequency-gain response was modified. The difference between the final REIG and the NAL-NL1 target REIG was recorded as final target mismatch. RESULTS: Of the 51 initial fittings, 36 (71%) failed to achieve a match within ±10 dB of the NAL-NL1 insertion gain target at 1 or more frequencies between 0.25 and 4 kHz. After the authors adjusted the frequency-gain response of the hearing aids, only 9 fittings (18%) failed to achieve a match. CONCLUSION: These outcomes suggest that target insertion gains for the open-fit hearing aids used here are rarely achieved with a first fitting but can usually be achieved through adjustments based on REIG measurements.

Real ear measurement methods for open fit hearing aids: modified pressure concurrent equalization (MPCE) versus modified pressure stored equalization (MPSE).

OBJECTIVE: The aim of this study was to assess differences between real ear insertion gains (REIG) measured with the modified pressure concurrent equalization (MPCE) and modified pressure stored equalization (MPSE) methods for open fittings in a typical audiology patient population. DESIGN: REIGs were compared for the two methods using a warble tone sweep at 65 dB SPL. The differences between the two methods at 0.25, 0.5, 1, 2, 3, 4 and 6 kHz were recorded. STUDY SAMPLE: Eighty-three ears of a consecutive sample of 48 candidates for open-fit hearing aids were included. RESULTS: The mean difference between MPSE and MPCE REIGs was less than 1 dB at all frequencies. Analysis of variance showed that the main effect of method was not significant, and there was no significant interaction between method and frequency. CONCLUSIONS: The results for the MPSE and MPCE methods did not differ significantly for the patients with mild-to-moderate hearing losses tested here, for whom REIGs were generally less than 20 dB. Further research is needed to identify the REIG values at which the differences between MPCE and MPSE methods become clinically significant.

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.

Is there evidence that environmental noise is immunotoxic?

Noise is a stressor. Noise-induced stress can lead to release of stress hormones. Acute stress whether physical or psychological is necessary for adaptation to change. However, chronic stress can lead to the persistent elevation of hypothalamic-pituitary-adrenocortical hormones, which are detrimental to health and can lead to disease states. It has also been suggested that there may be multiple interactions between the sympathetic and the complex feedback neuroendocrine systems, which interact with the immune system, in the genesis of the observed effects. Thus noise stress may be a factor contributing to the mechanisms of noise-induced hearing loss through alterations in the cell-mediated immune response. Other than the noise stress acting directly, it may also have an impact on the immune function via noise-induced sleep deprivation. Furthermore, recent evidence indicates that the immune function may be modified by conditioning techniques, perceived control, or the individual's ability to cope with stress-inducing factors. This suggests a possible means of alleviating the stress-induced effects. This review will examine the current available data on the effects of chronic environmental noise exposure on immune function.

Heavy metals and noise exposure: health effects.

Heavy metals are chemical elements with a specific gravity that is atleast five times that of water which is 1 at 4 degrees C. The commonly encountered heavy metals are lead,mercury, cadmium, and arsenic. Lead levels in children continue to be a health hazard as the current limit of 10 ug/dL is considered too high with the WHO estimate of 40% of children having blood levels greater than 5 ug/dL. Some authors have suggested a new limit should be set at 2 ug/dL. There are substantial differences in the literature regarding the effects of lead on hearing as assessed by pure tone audiometry. Mercury causes hearing loss and neurological dysfunction in Humans and animals. Methyl mercury is considered a more toxic compound to mercuric chloride. Cadmium causes a range of health effects from lung cancer, kidney damage to hearing loss. Dose dependent effects on hearing loss have been shown in rats. Combined effect with noise exposure has been shown to be more pronounced. Arsenic is released into the environment through the smelting process of copper, zinc, and lead. It is usually found in the water supply. Hearing impairments have been noted in the low and high frequencies in conjunction with balance disturbance.

Auditory efferent function is affected in multiple sclerosis.

OBJECTIVE: This study evaluated efferent medial olivocochlear (MOC) function in patients with multiple sclerosis (MS). Various afferent auditory abnormalities have been described in MS, but there is a paucity of data on efferent function. The brain stem is a site of predilection for MS plaques and the efferent MOC pathway may be affected at this level. METHODS: The study included 30 patients who had normal hearing. According to MRI findings, they were divided into two groups: those with an identifiable brain stem lesion (n = 10) and those with MS lesions in other parts of the central nervous system but without demonstrable MS plaques in the brain stem (n = 20). MOC function was evaluated by the olivocochlear suppression test, using transient evoked otoacoustic emissions. All subjects underwent standard auditory tests, including pure-tone audiometry and recording of auditory brain stem evoked responses. Twenty-two healthy subjects with normal hearing, matched for age and gender, served as a reference group for the auditory data. RESULTS: The results showed that 66.6% of all patients had reduced MOC function, particularly those (90%) with identified lesions of the brain stem on MRI. Furthermore, abnormal MOC function was found in 55% patients without evidence of a brain stem lesion on MRI. CONCLUSIONS: This study provides the evidence for a deficit of efferent auditory function in the majority of patients with MS. Taking into consideration the possible roles of the MOC system in processing of auditory information, abnormal MOC suppression in patients with MS may explain a variety of auditory presentations that are currently largely overlooked. This study also highlights the diagnostic value of the MOC suppression test as a site-of-lesion diagnostic test in MS and in identifying subtle brain stem lesions undetected by MRI, suggesting that subtle brain stem lesions may exist and that the MOC suppression test is sufficiently sensitive to detect them. Accordingly, the MOC suppression test may provide a tool for an early diagnosis of MS.

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.

Effects of industrial solvents on hearing and balance: a review.

Industrial hearing loss has generally been associated with noise exposure, but there is a growing awareness that industrial solvents can have an adverse effect on the auditory and vestibular systems in man. Both animal experiments and human studies point to an ototoxic effect of industrial solvents, as well as some central auditory and vestibular disturbances. This review examines the research from the last four decades in an attempt to get an overview of the available evidence. Research shows that industrial solvents are ototoxic in rats. The majority of the solvents studied cause a loss of auditory sensitivity in the mid-frequencies in rats, affecting outer hair cells in the order OHC 3 > OHC 2 > OHC 1 . Inner hair cells are generally unaffected. Spiral ganglion cells are most vulnerable to trichloroethylene. Simultaneous exposure to solvents and noise results in a synergistic effect; the pattern of trauma mirrors that due to solvent exposure rather than noise, but is more enhanced. There is a critical level when synergy occurs. The effects of solvents on the vestibular system are neurotoxic and influence the vestibulo-oculomotor system in both animals and humans; humans also present with problems in postural sway. There is a strong suggestion from human studies that solvents are ototoxic in man, but findings show that both the peripheral and central auditory pathways can be affected. Hearing losses can be in the high frequency region or can affect a wider range of frequencies. Hearing loss and balance disturbances can occur at levels below permitted levels of exposure. The synergistic effect of combined exposure to solvents and noise has also been noted in humans, resulting in greater hearing losses than would be expected from exposure to noise and solvents alone. The findings from both human and animal studies indicate that exposure to industrial solvents or to industrial solvents and noise can have an adverse effect on hearing and balance. The implications for industry and hearing conservation are far reaching.

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.

Effect of exposure to a mixture of solvents and noise on hearing and balance in aircraft maintenance workers.

Aircraft maintenance workers are exposed to a mixture of solvents in the presence of intermittent noise. For this study these workers exposed to solvent mix and noise, were compared with mill workers exposed to noise alone, printed circuit board operatives exposed to solvents alone and those exposed to none who acted as controls. Tympanometry, acoustic reflex thresholds, transient and distortion product otoacoustic emissions, auditory brainstem potentials, nystagmography and posturography were examined. There was a significant effect on pure tone thresholds for both noise and solvents+noise. The distortion product otoacoustic emissions declined with frequency and exhibited lower DP amplitude with noise compared to solvents and noise group. The transient emissions showed a similar effect. Over 32% of subjects with solvent and noise exposure had abnormalities of the auditory brainstem responses in terms of interwave interval prolongation. The mean acoustic reflex thresholds showed a pattern of differences which differentiate noise from solvent and noise groups. The contralateral pathway appears to be differentially affected by solvent exposure. 32% of subjects in the solvents and noise group had an abnormal posturographic finding. In the solvents and noise group 74% had abnormalities of saccades, 56% of pursuit and 45% of optokinetic nystagmus.

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.

Solvents impair balance in Man.

Solvents are commonly used in many industries and therefore exposure to multiple solvents is a common occupational hazard. A myriad of peripheral and central nervous system toxic effects can be produced by both acute and chronic low level exposures. Dizziness is often an early symptom of solvent exposure but has only in recent times been investigated specifically. The indications from the studies reviewed are that vestibular disturbances are common in workers exposed to solvents and dose-response relationships need to be established for early detection of vestibulo-toxicity.

Tinnitus induced by occupational and leisure noise.

Noise exposure is the most common cause of tinnitus. Noise induced permanent tinnitus (NIPT) can derive from occupational noise exposure, leisure noise or acoustic trauma. In general NIPT is high - pitched and tonal. The most common observed frequency of tinnitus on pitch matching is the same as the worst frequency for hearing. The sensation level of NIPT is usually low and sometimes negative. There is no correlation of significance between the discomfort caused by NIPT and audiometric findings. In occupational NIPT the interval between the start of noisy work and the appearance of tinnitus is long (many years) but with leisure noise and acoustic trauma the interval between exposure and tinnitus is frequently very short (immediate). It is a problem that the incidence of musically induced tinnitus is increasingly more common. It is also a much greater handicap for a young individual to suffer from tinnitus than from a small high tone hearing loss. Much more attention needs to be given to improve these matters. The treatment of NIPT is not different from tinnitus treatment in general.