A Rationale for the population study

A Self-reported hearing problems

B Prevalence of tinnitus

C Reported noise exposure

i Extent of hearing disorders

Many of the estimates for population prevalence and clinical incidence of hearing disorders in the UK (e.g. Shepherd, 1978) cannot be usefully interpreted because either the assumptions on which they are based are untenable or because imprecise definitions of hearing disorders have been used. Even where available, service statistics such as patient attendances are difficult to interpret even as estimates of incidence because they are based on purely otological diagnosis (at best upon the WHO International Classification of Diseases) and are hence totally inadequate for assessing the auditory status of patients. Also those who do present for treatment may be considered not to be representative of the population (Davis, in press). In particular, those with a mild to moderate hearing loss do not come forward for assistance unless their hearing loss is compounded by limitations in their central information processing capacity (Hayes and Jerger, 1977) which, if anything, limits the extent to which they can then be helped.

Estimates of prevalence based on service statistics face similar problems. In particular local differences in the system for the treatment of hearing disorders makes a unified account of health care statistics relating to those disorders impossible. Furthermore, it is often the case that hearing disorders are secondary to respiratory, infective or neoplastic disease (Patrick et al., 1981; MacLean, in press; Leske, 1981) and consequently both in clinical records and in surveys, a hearing disorder may not be recorded. This is especially the case in surveys of general health (e.g. in the General Household Survey) and in some surveys of disability, where the questions are often imprecise about the nature and extent of hearing losses.

In the UK, the last major survey of hearing disorders in the population was the model study of Wilkins (1948), which is now rather dated; it did not use any audiological measurements but used a questionnaire “calibrated” in a different population to assess hearing loss. The MRC Institute of Hearing Research (IHR) is coducting the NSH to overcome the above drawbacks; it ensures adequate measurement by being able to call on the services of scientific and technical audiological personnel as well as medical (otological) screening and cover. This means we can document precisely the otological and audiological status of specified samples from the population as well as the demographic and possible causal factors involved in the hearing disorders. This will enable us to generalise the broader implications of our results, and some of the finer associations within them, beyond the population of immediate concern in the UK. For example the factors influencing hearing disorders such as age have value for generalising from one population to another once key variables such as the age structures are known.

ii Understanding of hearing disorders

Although the population audiometric profile is of practical value, it has a rather limited scientific interest. At present it appears possible to enhance the understanding of hearing disorders in three main ways. We may extend our appreciation of their causes, we may improve their description in physiological or communication-science terms, or we may appreciate the differential consequences they may have. Any improvements in legislation, in either preventive or responsive medical services and in overall rehabilitative provision (or possibly detailed procedures) must follow from the appraisal of knowledge in each of these domains, rather than from an increase in one alone. Because knowledge is best applied societally in such a multi-domain fashion it is necessary for the knowledge itself to be acquired and structured within a framework that acknowledges the separate domains. Such a framework is outlined in Section IAiii and Fig. 1. It follows from this framework that it is important to assess individuals in domains other than those tapped by their hearing sensitivity (see also Lutman, 1982; this volume).

iii Schema for hearing dysfunction

There is a need for audiologists to learn from and align themselves with those who deal with impairment, disability and handicap in other specialties e.g. vision and mobility. To facilitate such alignment the World Health Organisation has recommended a standard terminology, which we have adopted. This is particularly necessary as medical terminology largely presupposes that the underlying disorder is, in some anatomical and patho-physiological sense, known; this is often not the case in auditory dysfunction. Much of the work leading to the adopted terminology was undertaken by Wood (WHO, 1980; Wood, 1980). I have expressed the terminology as a schema for auditory dysfunction in Fig. 1 urged by Duckworth (in press) closely following the schema of Colenbrander (1977) for dimensions of visual performance. An array of concrete examples in each domain is provided plus the type of remedial action currently appropriate to alleviate or minimise dysfunction. It is obvious from Fig. 1 that any particular measurement taken or report received from a patient...