Prevalence of the commoner ear, nose, and throat conditions in the adult rural population of Great Britain. A study by direct examination of two random samples

Hearing in Adults: A Digital Reprint of the Main Report From the MRC National Study of Hearing

The 1011-page book, Hearing in Adults, published in 1995, contains the fullest report of the United Kingdom’s Medical Research Council National Study of Hearing. It was designed to determine the prevalence and distribution in Great Britain of audiometrically measured hearing loss as a function of age, gender, occupation, and noise exposure. The study’s size, quality, and breadth made it unique when it was done in the 1980s. These qualities remain, and its data are still the primary U.K. source for the prevalence of auditory problems. However, only 550 copies were printed, and the book is essentially unobtainable today. We describe here a fully searchable, open-access, digital (PDF) “reprinting” of Hearing in Adults, summarizing the study’s design and the book’s contents, together with a brief commentary in the light of subsequent developments.

Tinnitus, unipolar brush cells, and cerebellar glutamatergic function in an animal model

Unipolar brush cells (UBCs) are excitatory interneurons found in the dorsal cochlear nucleus (DCN) and the granule cell layer of cerebellar cortex, being particularly evident in the paraflocculus (PFL) and flocculus (FL). UBCs receive glutamatergic inputs and make glutamatergic synapses with granule cells and other UBCs. It has been hypothesized that UBCs comprise local networks of tunable feed-forward amplifiers. In the DCN they might also participate in feed-back amplification of signals from higher auditory centers. Recently it has been shown that UBCs, in the vestibulocerebellum and DCN of adult rats, express doublecortin (DCX), previously considered a marker of newborn and migrating neurons. In an animal model, both the DCN, and more recently the PFL, have been implicated in contributing to the sensation of acoustic-exposure-induced tinnitus. These studies support the working hypothesis that tinnitus emerges after loss of peripheral sensitivity because inhibitory processes homeostatically down regulate, and excitatory processes up regulate. Here we report the results of two sequential experiments that examine the potential role of DCN and cerebellar UBCs in tinnitus, and the contribution of glutamatergic transmission in the PFL. In Experiment 1 it was shown that adult rats with psychophysical evidence of tinnitus induced by a single unilateral high-level noise exposure, had elevated DCX in the DCN and ventral PFL. In Experiment 2 it was shown that micro-quantities of glutamatergic antagonists, delivered directly to the PFL, reversibly reduced chronically established tinnitus, while similarly applied glutamatergic agonists induced tinnitus-like behavior in non-tinnitus controls. These results are consistent with the hypothesis that UBC up regulation and enhanced glutamatergic transmission in the cerebellum contribute to the pathophysiology of tinnitus.

Occupational exposure to noise and the attributable burden of hearing difficulties in Great Britain

AIMS

To determine the prevalence of self reported hearing difficulties and tinnitus in working aged people from the general population, and to estimate the risks from occupational exposure to noise and the number of attributable cases nationally.

METHODS

A questionnaire was mailed to 22 194 adults of working age selected at random from the age-sex registers of 34 British general practices (21 201 subjects) and from the central pay records of the British armed services (993 subjects). Information was collected on years of employment in a noisy job; and whether the respondent wore a hearing aid, had difficulty in hearing conversation, or had experienced persistent tinnitus over the past year. Associations of hearing difficulty and tinnitus with noise exposure were examined by logistic regression, with adjustment for age, sex, smoking habits, and frequent complaints of headaches, tiredness, or stress. The findings were expressed as prevalence ratios (PRs) with associated 95% confidence intervals (CIs). Attributable numbers were calculated from the relevant PRs and an estimate of the prevalence of occupational exposure to noise nationally.

RESULTS

Some 2% of subjects reported severe hearing difficulties (wearing a hearing aid or having great difficulty in both ears in hearing conversation in a quiet room). In men, the prevalence of this outcome rose steeply with age, from below 1% in those aged 16-24 years to 8% in those aged 55-64. The pattern was similar in women, but severe hearing loss was only about half as prevalent in the oldest age band. Tinnitus was far more common in subjects with hearing difficulties. In both sexes, after adjustment for age, the risk of severe hearing difficulty and persistent tinnitus rose with years spent in a noisy job. In men older than 35 years with 10 or more years of exposure, the PR for severe hearing difficulty was 3.8 (95% CI 2.4 to 6.2) and that for persistent tinnitus 2.6 (95% CI 2.0 to 3.4) in comparison with those who had never had a noisy job. Nationally, some 153 000 men and 26 000 women aged 35-64 years were estimated to have severe hearing difficulties attributable to noise at work. For persistent tinnitus the corresponding numbers were 266 000 and 84 000.

CONCLUSIONS

Significant hearing difficulties and tinnitus are quite common in men from the older working age range. Both are strongly associated with years spent in a noisy occupation--a predominantly male exposure. The national burden of hearing difficulties attributable to noise at work is substantial.

Ear wax removal: a survey of current practice

OBJECTIVE

To determine the methods of removing ear wax used by local general practitioners and the incidence of associated complications.

DESIGN

Postal survey of 312 general practitioners serving a population of about 650,000; supplementary study of ear, nose, and throat outpatients to quantify the improvement in aural acuity after wax removal.

SETTING

Catchment area of the Edinburgh otolaryngological unit.

PARTICIPANTS

289 General practitioners who responded to the survey; 21 outpatients in the ear, nose, and throat department with occlusive wax.

RESULTS

274 General practitioners removed wax by syringing, but only 53 (19%) always performed the procedure themselves; the remainder routinely delegated the task to practice nurses, some of whom had received no instruction. Ears were rarely examined again after the procedure. Complications had been experienced by 105 practitioners (38%) and included perforation, canal lacerations, and failure of wax removal. The removal of occlusive wax improved hearing by a mean of 5 dB over the frequencies analysed.

CONCLUSIONS

About 44,000 ears are syringed each year in the area and complications requiring specialist referral are estimated to occur in 1/1000 ears syringed. The incidence of complications could be reduced by a greater awareness of the potential hazards, increased instruction of personnel, and more careful selection of patients.

Ménière's disease. A practical approach to management

The management of Ménière's disease continues to provide a formidable clinical challenge, mainly because its precise aetiology is unknown. The unpredictable natural history of the condition has consistently bedevilled attempts to evaluate therapeutic efficacy, and there have been no entirely satisfactory prospective controlled clinical trials of any specific medical or surgical treatment. Although no form of medication has been convincingly shown to influence the long term course of the disease, many drugs may be useful in the control of vertigo. In recent years conservation of hearing has assumed equal importance to the control of vertigo as the therapeutic goal. Indications for conservative endolymphatic sac surgery, which appears to offer the best prospect of preventing the progressive deafness which invariably accompanies the established condition, are discussed. The necessity for a flexible therapeutic approach to the management of Ménière's disease is underlined.

Deafness in middle age--how big is the problem?

Screening for hearing defect by questionnaire and audiogram was undertaken in two group practices in the South-east of England in a total of 2,278 people aged 40-64 years.The prevalence of deafness in the combined populations of these two practices as measured by audiogram was found to be 5.8 per cent (+/- 0.5 per cent; one standard error). This figure is much more than estimates derived from American data for use in Britain. The prevalence of deafness was shown to increase with lower social class and age. The questionnaire was found to be unreliable for prevalence studies, but was thought to have some use as a screening instrument.There was an incidental finding of increased hearing defects in the left ears of men. The firing of rifles was felt to be a possible explanation of this.