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I am a Senior Audiologist by profession who qualified with a British Masters degree (University College London, 2004) and an American Doctorate degree (NOVA Southeastern University, 2006), both in Audiology. I have practised Clinical Audiology for more than six years and I work closely with Otolaryngology doctors/surgeons both in clinical procedures and research. At present (2010), I am pursuing a Master...
I am a Senior Audiologist by profession who qualified with a British Masters degree (University College London, 2004) and an American Doctorate degree (NOVA Southeastern University, 2006), both in Audiology. I have practised Clinical Audiology for more than six years and I work closely with Otolaryngology doctors/surgeons both in clinical procedures and research. At present (2010), I am pursuing a Masters degree in Public Health at Manchester University Medical School.
I read with both interest and controversial scepticism on the large scale population-based study on the 'Prevalence and Characteristics of hearing problems in a working and non-working Swedish population' recently published in J Epidemiol Community Health 2010:64:453-460. I wish to highlight potential erratum or flaws concerning the said 'health issue' of hearing problems, in-hope of inferring a meaningful interpretation of the study's findings that are relevant to Public Health Practice.
Firstly, the definition of 'hearing problems' in the study, as referenced to the World Health Organisation's (WHO) statement of "being among the top 10 most common burdens of disease in medium and high income countries", was intended to refer to the pathophysiology of sensorineural / cochlear or inner ear hearing loss (Mathers and Loncar, 2006; Mathers et al, 2000).
According to the WHO published definitions (Mathers and Loncar, 2006; Mathers et al, 2000) and to the Professional bodies of the British Academy of Audiology (BAA) and the American Speech-Language Association (ASHA), sensorineural hearing loss refers to 'a permanent and irreversible damage to the sensory hair cells found inside the peripheral end organ in hearing' called the cochlea that is predominantly caused by natural deterioration in old-age (presbyacusis), by noise-damage, and also by ototoxic medications. These aetiologies can concur at the same time and synergistically worsen sensorineural hearing loss (e.g. old aged patients with previous occupational or recreational noise-exposure). Other less common causes of sensorineural hearing loss include congenital, syndromal, or hereditary causes, idiopathic sudden hearing loss, or Otoneurotological pathologies coupled with vestibular symptoms (e.g. Acoustic tumours).
Not so relevant to the scope of this definition are the "conductive hearing loss" cases, which refer to middle ear pathologies managed by doctors / surgeons specialising in Otolaryngology. More irrelevant, are the "central processing disorders", which refer to problems along the neuro-auditory or cognitive pathways, or psychological difficulties and/or mental alertness or orientation issues, unless it is a Psychiatric, Psychological, or Mental Health disorder at hand.
In the study however, the first outcome measure used in the questionnaire was a subjectively self-reported difficulty "to hear what is said in a conversation between several persons" (Hasson et al, 2010). The question is vague and presents a big dilemma because it may refer to a 'one-off incident of not hearing something' (e.g. absent-mindedness), a 'normal phenomenon of missing one word or two in a conservation', or anything referring to central auditory processing issues of speech-in- noise problems without proper clinical documentation or diagnostic evidence of dysfunction or impairment.
Secondly, tinnitus that is typically considered as clinically relevant and debilitating to the patient is a constant, non-ceasing, continuous tinnitus day and night, which may occur unilaterally or bilaterally and in varying degrees of loudness and frequency / type such as buzzing, swooshing, whistle, etc (British Tinnitus Association).
In the study however, the second outcome measure in the questionnaire was a subjective self-reported questionnaire on tinnitus "lasting more than 5minutes" (Hasson et al, 2010). It is clinically considered a normal phenomenon to have 'Spontaneous Tinnitus' in healthy individuals, which occurs and disappears spontaneously. Individuals truly suffering with debilitating tinnitus report of constant tinnitus that affects their sleep and/or daily activities (McKenna and Gardner, 2009).
Given the above flaws in the pathophysiology definition of hearing problems, there are dilemmas arising in the interpretation of the studied 'public health issue' and to the recommendations for interventions or preventions.
The intended objective of the study was to compare the prevalence of hearing problems and tinnitus in the working and non-working population by grouping the samples from one common population source in Sweden. It is not surprising to find very closely similar prevalence results in both the working and non-working groups's (proportion or percentage %) distribution of tinnitus and severity and discomfort of tinnitus, and prevalence of hearing loss and of hearing problems (see Hasson et al, 2010; Table 1 and 2). Also, no test of population heterogeneity or comparative difference was conducted between the working and non-working groups. There is no statistical test to demonstrate any difference between the two groups, which poses a serious flaw to the conclusion that hearing problems (tinnitus and hearing loss) are "by far more prevalent than previously estimated" when it is not supported by any found evidence showing a higher prevalence. Therefore, there is a high probability that both the working and the non-working populations may be homogenous groups belonging to the same population and sharing the same characteristic risks or self-reported complains of "hearing problems" as outcome measure.
There is also vagueness in the Public health related recommendation that "tailored preventive interventions need to be implemented at individual, organisational as well as societal levels" (Hasson et al, 2010). It is common knowledge to healthcare practitioners, and public health experts that both the working and non-working populations are at risk to hearing problems when exposed to noise or individuals who incur age-related problems
From a health protection point of view, there are already existing organisational and societal preventative interventions targeted at occupational and recreational damaging noise exposure. Existing measures and policies in the European Legislation already address environmental noise pollution (EU Directive 2002/49/EC), occupational health risks for work environments (EU Directive 2003/10/EC) and recreational risks to young adults, e.g. music players / disco club noise risks (EU Scientific Committee on Emerging and Newly Identified Health Risks SCENIHR, 2008).
From a healthcare provision and policy point of view, there remains no surgical or medical treatment to 'cure' constant tinnitus or permanent sensorineural hearing loss, except for middle ear pathologies and infections managed by Otolaryngology surgeons or doctors. No prevention can avoid risks or problems of age-related hearing difficulties, except by interventions of providing hearing aids use. Limitations and cost-benefit analysis coupled to diagnostic and rehabilitative interventions are considered in these respects.
Finally however, the study generated two important new findings which are - the link between socioeconomic (employment) status and self-reported hearing problems, and the highlighted findings for young adults aged below 40. The results found a "clear socio-economic gradient in the prevalence of hearing problems, where lower status is more affected", as well as finding that "approximately every fifth of young adult below 40 years of age to have either tinnitus or hearing loss"(Hasson et al, 2010). These may be of high importance for demographic targeting in Health Promotions or Health Communications for raising public awareness for occupational and recreational risks in noise-induced hearing loss
1. Hasson D, Theorell T, Westerlund H, Canlon B. Prevalence and
Characteristics of hearing problems in a working and non-working Swedish
population. J Epidemiol Community Health 2010; 64:453-460
2. Mathers CD, Loncar D. Projections of global mortality and burden
of disease from 2002 to 2030. PLoS Med 2006;3(11):e442 (also found online:
accessed 11th October 2010).
3. Mathers C, Smith A, Concha M. Global Burden of hearing loss in
the year 2000. Global Burden of Disease. Geneva: World Health
Organization, 2000:1-30 (also found online:
19th October 2010).
4. British Academy of Audiology website: Accessed 19th October 2010.
5. American Speech-Language Hearing Association website: Accessed
19th October 2010. (http://asha.org/)
6. British Tinnitus Association website: Accessed 10th October 2010
7. McKenna L and Gardner C (2009). Good Night Sleep Tight. British
Tinnitus Association (also found online:
accessed 17th October, 2010)