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|Year : 1999 | Volume
| Issue : 2 | Page : 3--6
Is it still necessary to conduct research on noise-induced hearing loss?
National Institute for Occupational Safety & Health, Division of Biomedical and Behavioural Science, 4674 Columbia Parkway, Cincinnati OH 45226, USA
National Institute for Occupational Safety & Health, Division of Biomedical and Behavioural Science, 4674 Columbia Parkway, Cincinnati OH 45226
|How to cite this article:|
Morata T. Is it still necessary to conduct research on noise-induced hearing loss?.Noise Health 1999;1:3-6
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Morata T. Is it still necessary to conduct research on noise-induced hearing loss?. Noise Health [serial online] 1999 [cited 2020 Sep 26 ];1:3-6
Available from: http://www.noiseandhealth.org/text.asp?1999/1/2/3/31710
In conferences, scientific meetings and publications which focus on noise and its effects, it is common to hear that sufficient knowledge in this area is available for noise-induced hearing loss to be prevented and not therfore an issue of concern in occupational health. Unfortunately, basic research concerning the mechanisms of noise-induced hearing loss do not translate into promptly effective prevention programs for populations at risk. For this reason, it is as common to hear that noise-induced hearing loss still remains in the list of the most prevalent work-related conditions in most industrialised countries (van der Venner, 1992; Merry and Franks, 1995; Barrenas et al., 1996). This scenario points to the need for an examination of what research has been done, and what is lacking.
Recent Evaluations of Research Needs
The examination of research needs arise periodically either following financial constraints or pressure from specific groups in society with a particular need. Usually, panels of experts (which can be inclusive or very restrictive) examine the situation and define new goals.
Some of the more inclusive approaches, such as the Delphi technique, have been used to identify needs in the areas of otorhinolaryngology and occupational health (Harrington, 1994; van der Beek et al., 1997, Rudy et al., 1998). The Delphi technique is a survey process that normally includes the acquisition of: a) anonymous opinions from members of an expert group by formal questionnaire or individual interview, b) several rounds of systematic modifications/criticisms of the summarised anonymous feed-back provided to the groups and c) a group response by aggregation (often statistical) of individual opinions on the final round (Adler and Ziglio, 1995). Among the examples cited earlier in this paragraph, the survey of United Kingdom medical opinion on research priorities in occupational medicine, identified specific outcomes that still required research, and among those, hearing loss.
However, the most common approach still relies on the examination of statistics related to the occurrence of noise-induced hearing loss (Luxon and Prasher, 1996; Barrenas et al 1996, Sulkowski et al., 1996. NIOSH, 1996). Both in Europe and the US, noise-induced hearing loss is still among the most prevalent work-related conditions.
Initiatives in Europe
Barrenas et al. (1996) reviewed hearing conservation practices in Europe, and described a scenario that much resembles practices in the US. In most European countries, the professionals that perform audiometric testing have limited training, and can offer the worker/patient very little information about his or her hearing status or regarding hearing loss prevention. Training programs were also reported as being insufficient or inadequate, which was considered as one of the weakest points of current hearing loss prevention programs. Specifically in Sweden, there was a reduction in cases of noise-induced hearing loss during the 1970's and 1980's, but in the following decade an increase in the prevalence of hearing loss was registered. The authors suggested that one of the reasons for this was that resources for occupational health centres were cut at that time. Producers of hearing protectors indicated that the sales of hearing protectors has increased in Europe, especially in Scandinavia, but no information on their utilisation is available. In an ongoing research project in Sweden, which is being conducted mainly in small companies, periodic hearing tests were only offered in 2 of the 11 companies studied, despite excessive noise levels measured in 10 of the companies, and the observation of high prevalence of hearing loss (Johnson et al., in preparation). Nevertheless, the Swedish National Institute for Working Life (former National Institute for Occupational Health), plans to concentrate their future research efforts on the non-auditory effects of noise, particularly on annoyance (see institute's publications or website).
Having recognised the need for research on noise-induced hearing loss, the need to facilitate interaction between research centres to expedite results and increase their impact in changing the current scenario, the European Commission has funded a concerted action named Protection Against Noise (PAN). The PAN initiative is the result of an ambitious project put together by Prasher and Luxon (1996) from University College London, which brought together 52 partners from 17 European countries to collaborate on the subject of noise and hearing conservation. Their activities are not restricted to occupational noise exposure and its effects, but they constitute the core of their collaborative effort. The various teams are covering different aspects from acoustics of noise-induced hearing losst to clinical identification, susceptibility, risk factors, the interaction of different pathological processes within the cochlea, to effective preventive measures and rehabilitation. As part of the PAN initiative, the Noise Research Network (publisher of this journal) was established. It should outlive PAN and further develop.
Initiative from the World Health Organization (WHO)
In 1997, the Programme for the Prevention of Deafness and Hearing Impairment of the World Health Organization, organised a meeting of experts from developed and developing countries in order, not only to assess research needs, but also to seek methods for prevention (WHO, in press). Occupational setting is still viewed as the main source of excessive noise, but environmental and leisure settings are also recognised as sources of significant risk. Overall, exposures were reported to be escalating, along with the risk of hearing impairment.
Despite the scarcity of reliable and comprehensive statistics from developing countries, the experts have indicated that the risk for hearing loss seemed to be increasing even more dramatically than in developed countries. Participants from developing countries such as Pakistan, India, Thailand, Kenya, Ghana, Egypt and Brazil stressed the insufficiency or nonexistence of preventative measures.
The panel identified the following research priorities: study of the molecular and biochemical mechanisms of NIHL, cochlear pharmacology and intervention, research on hearing protectors, and studies on the risk factors, including susceptibility. Moreover, the need for the development or improvement of prevention initiatives, for an increase in the awareness of risk from noise, improvement of the training of health personnel, and gathering of epidemiological data were also listed as recommendations for action (WHO, in press).
Initiative from the United States National Institute for Occupational Safety and Health (NIOSH)
Specifically in the occupational arena, much can be learned from a comprehensive evaluation of research needs conducted by the National Institute for Occupational Safety and Health (NIOSH). In early 1995, NIOSH launched an extensive consultation initiative to redefine research priorities for the following decade, not only for NIOSH, but also for the entire occupational safety and health community (NIOSH, 1996). This process is usually referred to by the name of its final product, the National Occupational Research Agenda or NORA (NIOSH, 1996). In the March issue of the American Journal of Public Health (1998) the reader can find a paper by Rosenstock et al. summarising the process and also an editorial by Wegman on its implications. The process was quite innovative, as it did not restrict the participation to the experts only. NIOSH made possible the input of all segments of the occupational safety and health community, including the targeted beneficiaries of NIOSH work. Through a consensus-building process, NIOSH identified research priorities after receiving input from in-house scientists, as well as from employers, employees, health officials and their professionals, scientists, and various types of organisations (public health, advocacy, scientific, industry, and labour). Approximately 500 organisations and individuals outside NIOSH contributed to the Agenda.
An initial planning working group of senior scientists from inside and outside NIOSH developed a list of 48 potential research topics. Subsequent working groups met in public forums to provide input and help identify priority research topics. Each group was allowed to modify the list by adding or merging topics as deemed appropriate. The priority list was not necessarily a consensus of the group, but it
reflected the collective knowledge and opinions of individuals in the group.
Twenty-one of the topics were identified as high priority based on seven criteria: seriousness of hazard (based on death, injury, disease, disability, and economic impact), number of workers, magnitude of risk, potential for risk reduction, expected trend in importance of research area, sufficiency of existing research, and probability that research will make a difference. The input received was evaluated with respect to the frequency of endorsement and the seven criteria used by the working groups to identify high-priority topics. The priorities reflect a remarkable degree of concurrence among the large number of participants, which was achieved through the work group discussion and clear established criteria (NIOSH, 1996). Hearing loss passed through this detailed scrutiny, and the arguments for it are summarised in NORA (NIOSH, 1996). In the US, it is estimated that more than 30 million workers are exposed to hazardous noise. The document briefly discusses the seriousness of the condition (hearing loss) and some reasons why after so much research has been conducted on noise, noise-induced occupational hearing loss is the most common occupational disease. It states that up to now, it has not been possible to create a sense of urgency about this problem.
Specific need in the research on work-related hearing include studies on: a) the hearing status of contemporary workers, b) factors other than noise that can contribute to the development of hearing loss, such as chemicals and heat; c) susceptibility; d) effective hearing loss prevention initiatives; e) the development and implementation of new technologies for controlling noise and improving hearing protector effectiveness; and f) on new methods to improve the efficiency of biological monitoring for hearing loss.
In recent years, decreasing budgets or demands on the scientific community for greater accountability and applicability of research results have motivated several evaluation initiatives on research needs on noise-induced hearing loss. These evaluations, conducted in different countries, using different approaches, have pointed out the continuing need for research on the condition. The strongest argument is still, unfortunately, the resilient high occurrence of the condition in industrialised countries. The agreement is not restricted to the realisation of the need, but also on the specific facets which merit funding and attention. In a time of easier and increased communication between scientific groups, and society, the contribution of these evaluation initiatives, which identified pressing issues, should facilitate change (or so I hope).
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