A study published last month in the journal JAMA Otolaryngol Head Neck Surgery flagged up huge variation in estimates of the economic impact of hearing loss in the US. The paper (here) assessed the cost of hearing loss to the US economy in terms of both direct medical expenditures and indirect costs associated with hearing impairment, and found that these estimates often differed by billions of dollars: from $1.8 to $194 billion for the cost of lost productivity, and a $3.3 to $12.8 billion range for excess medical costs.
Amongst other complex reasons, this could in part be due to the definitions and types of hearing loss used in different American studies – for example, the study showed that some research included measures of noise-induced or work-related hearing impairment, whilst others didn’t.
This issue of accurate reporting is also prescient in Europe where varying figures are used by different organisations, depending on the measurement criteria being employed. For example, some organisations and studies use the measurement for self-reported hearing loss which is 50 million people (10% of the EU population), which is also the figure which appears in the Eurotrak report, the seminal 2-3 yearly study of European data that is 50% funded by the BIHIMA members and is scheduled to be updated in 2018.
However, the World Health Organisation uses an estimate of the total EU hearing loss, taking account of those people who do not self-report and may not even be aware of their hearing impairment – this is 80 million people (16% of the population). This is also the figure used by our European counterpart EHIMA and in research by Inga Holube and the National Institute on Deafness and Other Communication Disorders (NIDCD).
Both figures are useful for different purposes. The former lower figure is a good indicator of how motivated people are to seek hearing care, as well the efficiency of various distribution systems, whilst the latter figure is a better gauge of the big picture impact of hearing loss.
There are also some variations in the definitions of hearing impairment used by different organisations. In some cases, mild hearing impairment is assumed to start at a BEHL (Better Ear Hearing Level) of around 20dB, while other organisations consider hearing loss of up to 25dB to constitute ‘normal’ hearing. The influential Bridget Shield study, for example, which is published every 6 years and funded by our European counterpart EHIMA (with the new report due in 2018) supports the 25dB figure as being carefully “chosen by audiologists who deal with this problem every day”.
The table below shows just how much definitions of hearing loss can vary:
|Organisation||None||Mild||Moderate||Moderate – severe||Severe||Profound|
|World Health Organisation|
(avg. 0.5, 1, 2, 4 kHz)
| 25||26 – 40||41 – 60||61 – 80|| 81|
(avg. 0.5, 1, 2, 4 kHz)
| 20||21 – 39||40 – 69||70 – 94|| 95|
|American National Standards on Acoustics|| 26||27 – 40||41 – 55||56 – 70||71 – 90|| 91|
|Action on Hearing Loss||25 – 39||40 – 69||70 – 94|| 95|
|British Society of Audiology|
(avg. .25, .5,1,2,4 kHz)
|20 – 40||41 – 70||71 – 95||>95|
(avg. 0.5, 1, 2, 3 kHz)
|<25||~ 40|| 75|
We can see, then, that there is considerable variation in both qualitative and quantitative descriptions of hearing impairment, and it is important for policy-makers to be aware of these subtleties when assessing and managing the impact of hearing loss.