«THE ECONOMIC IMPACT AND COST OF HEARING LOSS IN AUSTRALIA A report by Access Economics Pty Ltd February 2006 Listen Hear! The economic impact and ...»
What is known presently is that some people succumb to hearing loss more readily than others (Biassoni et al, 2005) – the phenomenon of soft ears. In the absence of sufficient epidemiological data and attributable risk factors, it has not been possible in this study to estimate the number of people who may sustain RHL in the future.
Table 2-2 reports workers’ compensation claims for occupational hearing loss (OHL) over the six years to 2003.
TABLE 2-2: PAID WORKERS COMPENSATION CLAIMS FOR OHL, 1998-2003
Official rates for workers’ compensation claims for OHL have been falling in recent years, in the absence of any significant prevention programs. A notable fall is between 1998 and 1999 as shown in the table above. The most likely explanation for this is the introduction of a minimum threshold (also called a ’low fence’) for eligibility for compensation, introduced during the 1990s by various governments in response to rising workers compensation claims. 4 Prior to the introduction of a low fence, the average level of hearing loss from workplace noise was approximately 5%. This move culminated in a recommendation by the Heads of Workers Compensation Authorities (HOWCA, 1997:13) to recommend that in order to be eligible for compensation a worker must have a 10% hearing loss. While the height of the low fence differs between jurisdictions, low fences have been introduced in all jurisdictions, effectively reducing the number of people able to submit a claim for OHL.
While the Office of the Australian Safety and Compensation Council have developed a national standard for the control of OHL 5 and this standard has been widely adopted into state regulations 6, there is no nationally co-ordinated OHL prevention campaign.
4 The concept of the low fence refers to least level of impairment allowable before a person becomes eligible for compensation.
5 http://www.nohsc.gov.au/OHSLegalObligations/NationalStandards/NOISE.htm 6 http://www.workplace.gov.au/workplace/Category/Publications/WorkplaceRelations/WorkplaceRelations MinistersCouncil-ComparativePerformanceMonitoringReports.htm
The jurisdictions report monitoring noise exposures as part of the routine work ensuring occupational health and safety compliance and one-off, smaller scale projects are initiated in local settings. Periodically, there have also been campaigns targeting industry sectors, such as hearing loss prevention among farmers.
OHL is a slow onset condition and behaves in response to prevention efforts more like a chronic disease rather than an injury. In injury prevention, payback can be expected fairly soon after the program has been initiated. With OHL, it is reasonable that exposed workers over the age of 45 years will already have some degree of hearing loss. OHL prevention efforts target (1) reducing the severity of loss for those already affected and (2) preventing the onset of the condition in the next generation of workers.
ACOUSTIC SHOCK AND ACOUSTIC TRAUMA188.8.131.52
Two sources of hearing loss of current interest include acoustic shock and acoustic trauma. Acoustic shock is associated with the use of head sets in call centres while acoustic trauma is associated with acute, intense noise exposures.
Acoustic shock arising from head set use results from “a sudden and unexpected burst of noise transmitted through the call handler’s headset …the maximum output sound pressure level is limited to 118dB(A)” (Lawton, 2003:249). One Danish study reported that 22% of the workers in a call centre had experienced acoustic shock (Hinke and Brask, 1999). Acoustic shock may result in a temporary hearing loss (Milhinch, 2002). However, the extent to which it results in permanent damage to the auditory system is debated. Lawton (2003) observes that the noise emitted from headsets in the shock situation is not sufficient to cause permanent hearing loss. Furthermore, of the people studied, there were other explanations for any hearing loss they had sustained. Lawton does however observe that other debilitating effects are associated with acoustic shock including tinnitus (intermittent or prolonged spontaneous sounds in the ear) and psychological stress akin to post-traumatic stress disorder. Certainly emotional trauma is associated with the event as may be physical damage to parts of the inner ear, such as emergence of holes or fistulas occurring in parts of the hearing mechanism. What is particularly concerning but as yet not firmly established is the possible link between acoustic shock and the later development of Meniere’s Disease (Riotman et al, 1989; Di Biase and Arriaga, 1997; van der Laan, 2001; Segal et al, 2003). This disease impacts on the parts of the ear associated with balance. Episodes of the disease may be associated with the onset of hearing loss that is sensorineural in nature. However, there is no available epidemiological evidence that establishes a causal link or an association at the population level to allow estimates to be derived. The psychological sequelae resulting from acoustic shock warrants preventative efforts in its own right.
Acoustic trauma: Acute noise exposures associated with explosions such as bombs, localised alarm systems or artillery fire are common and known to result in hearing problems. Indeed, much of the modern development in hearing services resulted from the need to care for veterans following World War II (Henoch, 1979). While artillery fire may result in temporary hearing loss, for the majority of the population, repeated and preventable exposures are usually required before permanent hearing loss is sustained (Mrena et al, 2004).
However, current modelling scenarios for noise exposure and injury allow for the probability that, even within existing safe limits, 6% of people exposed may still sustain hearing damage (ISO, 1999). In such settings, the screening of people
with soft ears, may be indicated. Acoustic trauma is treated in this study within the population of people with noise-induced hearing loss.
Two models are commonly used to socially situate people with hearing loss.
The first is a medical-disability model. The vast majority of people with hearing loss acquire a mild to moderate hearing loss in adult life, with a small number of people acquiring deafness during childhood. People with acquired hearing loss commonly understand hearing loss as a sensory deficit within the body. For them, hearing loss can be appropriately described as a disability for which aids, devices and therapies are indicated. The most commonly reported consequence of hearing loss for this group is a loss of social participation such as being unable to follow conversations in noisy social settings. This group often finds hearing loss stigmatising and consequently they may less readily take up the services on offer or utilise commonly recommended communication strategies. For this group, hearing loss can be appropriately described within the context of a burden of disease model. Parents whose children are born deaf often identify with hearing culture and also view hearing loss within the medical-disability model.
The second model is a cultural-linguistic model. By contrast, people who are born severely to profoundly deaf may grow up in or later join the Deaf Community. Within the Deaf Community deafness is understood as a culturallinguistic experience. Deafness, rather than being a source of stigma is a source of pride and cultural identity. Members of the Australian Deaf Community communicate using Australian sign language known as Auslan. A common communication problem facing members of the Deaf Community is the inability of most Australians to converse with them in Auslan and the lack of availability of sign language interpreters. This group would define the social consequences of hearing loss in terms of reduced social participation in the broader community and encounters the impact of this in terms of socio-economic loss and reduced social interactions rather than perceiving it as a burdensome disease.
Irrespective of differing cultural constructions underpinning perceptions of deafness, people who experience deafness in some form encounter communication difficulties in specific social settings. Such difficulties can result in personal, health and social consequences. For some encounters, the Australian community has put in place remedies (eg schools for the Deaf, cochlear implant, sign language interpreters and hearing aid services) to redress the consequences of deafness.
This study examines the costs arising from such interventions and documents the net economic impact of people living with differing degrees of hearing loss in Australian society.
Hearing impairment does not necessarily equate to ‘disability’, ‘burden’ or ‘handicap’.
Noble (1991:60-63) points out that an assessment of the existence of a hearing loss in itself yields little information about the exact nature of the disability or social limitation experienced by the affected individual. A person's perception of the level of difficulty
caused by their hearing loss (what used to be called their hearing handicap, but now is defined in terms of social participation) may vary from individual to individual. By example, a lecturer with mild hearing loss may experience severe hearing handicap simply trying to interact with students in a lecture theatre – hearing loss reduces their capacity to work and relate effectively. Stressors are associated with this experience.
By contrast, a metal worker with advanced hearing loss living alone may experience little hearing handicap if he has few difficult communicative interactions.
Lutman et al (1987) observed that as the level of measured impairment increased, so too did the likelihood of communication difficulties. Cruickshanks et al (1998:881) report that the percentage of people reporting a hearing handicap increased with severity of loss – 5.5%, 19.7%, 47.5% and 71.4% for none, mild, moderate and severe losses respectively (p for trend.001). As such, people may choose to restrict their social, recreational or professional activities because of their hearing loss.
The degree of handicap or participation restriction is usually assessed using a self
report scale (Noble, 1991:60) states that:
"(W)ithout direct inquiry into the lives and circumstances of the people who manifest signs of impairment on these tests, little useful knowledge is gained about the disabilities (functional hearing incapacities in the everyday world) and none whatever about the handicaps (the disadvantages for everyday living) experienced as a consequence of the impairment".
Hawthorne and Hogan (2002) have shown that measures of hearing social participation are strongly associated with health related quality of life. Dillon (2001:368) observes that hearing loss is associated with a cascade of negative events.
“Hearing impairment decreases a person’s ability to communicate.
Decreased communication with others can lead to a range of negative emotions such as depression, loneliness, anxiety, paranoia, exhaustion, insecurity, loss of group affiliation, loss of intimacy and anger.” 2.5 BETTER EAR, WORSE EAR Hearing loss can differ from one ear to the other (asymmetrical hearing loss). As a result of this, prevalence rates can be reported for either the better or the worse ear in terms of the level of hearing loss. This presents a particular problem in hearing because almost a quarter of people with hearing loss have the impairment in only one ear (Wilson, 1997:96). Older right handed farmers, for example, often have hearing loss predominately in the left ear. This occurs as a result of looking over their right shoulder watching their work while driving older style tractors for extended hours, where the left ear is more directly exposed to the motor noise. A similar effect results from rifle shooting. As an individual takes aim down the barrel of a rifle, one ear is more exposed to the muzzle than the other (depending again on whether one is left or right handed). When the rifle is discharged, the ear nearer the muzzle has a higher noise exposure and in time greater hearing damage from repeated exposures.
Asymmetrical hearing loss results in problems such as difficulties with the spatial identification of sound (not being able to tell where a speaker’s voice is coming from), and auditory discrimination problems (picking up foreground sounds from background sounds) resulting in practical problems like not being able to function in meetings or social settings especially when people are on their ‘bad side’. Having better hearing in one ear than the other impacts on the ability to communicate and may lessen the
overall effect of the impairment in the worse ear. Given this outcome, disability in epidemiological hearing studies has been defined on measures of the better ear (Davis, 1989; Wilson et al, 1988), the approach also adopted in this study.
Differences in hearing difficulties rather than hearing loss are not expressed by an audiogram, although the level of hearing handicap may be "more highly correlated with measures of impairment in the worse ear than in the better ear" (Lutman et al, 1987:45When reporting prevalence rates, better ear measures would provide conservative estimates while worse ear measures may more accurately reflect impairment. This is a little different from visual impairment, where there is very little impairment experienced if vision loss occurs in one eye only.
In this study, the approach has thus been to report hearing loss prevalence for both the better and worse ear, but conservatively to use hearing loss prevalence in the better ear to attribute costs and disease burden. In addition, to distinguish the two, prevalence of hearing loss is used to refer to impairment in the worse ear, while prevalence of hearing disability is used to refer to impairment in the better ear.
This aligns with the Australian Institute of Health and Welfare (AIHW) approach, to avoid overstating the burden of disease on the community and adopt a minimum cost burden position.