Section 2.2 builds on the preventive actions to preserve hearing capacity that were outlined in Section 1 and focuses on actions to be taken at a population level to prevent hearing loss and ear diseases. Since certain health conditions or environmental influences are more likely to be experienced at particular stages of the life course, preventive strategies are designed to target these specific age groups. Many of these strategies, however, are applicable to multiple, or all, stages of a person’s life (Figure 2.1).
It is estimated that nearly 60% of hearing loss in children is due to avoidable causes such as vaccine-preventable diseases, ear infections, birth-related causes and
ototoxic medicines (1). The prevention of congenital and childhood hearing loss during prenatal and perinatal periods include:
IMMUNIZATION IN GIRLS AND WOMEN Vaccination against rubella prior to, or during, reproductive age is extremely effective in preventing congenital rubella in offspring (2, 3). Ongoing
research into the prevention of cytomegalovirus (CMV) infection is also encouraging, although as yet a vaccine is not available (4).
MATERNAL AND NEONATAL CARE
Antenatal maternal health and perinatal care are clearly linked with a child’s hearing status. Evidence
on the positive impact of improved antenatal and perinatal care on neonatal morbidity is unequivocal
(6). While there are no studies demonstrating a direct link between improved maternal care and hearing loss,
it is clear that such improved outcomes would also apply to hearing loss (7, 8).
In cases of mothers infected with syphilis, cytomegalovirus, toxoplasmosis or HIV, prompt
management can mitigate the risk of congenital hearing loss associated with these conditions (7, 9,
10). In addition, it is important to ensure that proper evidence-based protocols are followed for minimizing the ototoxic effects
of the medicines on the mother and her infant. The availability and use of appropriate resuscitation measures along with perinatal care for the prevention
and management of birth asphyxia, jaundice, and perinatal infections, minimizes the adverse consequences of these risk factors (11).
This contrasts with infants born in environments where health facilities are unavailable, or where health care is lacking, and who are thus at a greater risk for
immediate or delayed effects on their hearing trajectories throughout life. Awareness among health professionals of these risk factors, their association with congenital
hearing loss, and the common features that may indicate a hearing loss in an infant, can assist in early identification.
In families with a history of hearing loss, genetic counselling can prepare parents for hearing loss
in their offspring, and provide guidance for early identification and rehabilitation. Genetic counselling
refers to the provision of accurate information in a nondirective manner with the aim of offering
medical, psychological and social support (12). Such counselling services must always consider the
beliefs and values of deaf communities (13). Given the correlation between congenital deafness
and consanguinity, raising awareness in this respect and ensuring access to preconception and
premarital counselling services for consanguineous couples can help maintain and improve outcomes, including hearing loss prevention, identification and
management (14, 15).
2.2.2 CHILDHOOD AND ADOLESCENCE
Many of the risk factors for hearing loss and ear disease faced during early and late
childhood can be prevented or addressed.
IMMUNIZATION IN CHILDREN AND ADOLESCENTS
WHO estimates that over 19% of childhood hearing loss could be avoided by immunization against rubella and meningitis alone (1). Overall, vaccinations are highly
effective in protecting against common illnesses such as measles, mumps, rubella and meningitis, and thus can prevent hearing loss that occurs as a complication
(16, 17). The vaccine for measles, mumps and rubella (MMR) is shown to be highly effective in prevention (17, 18), and vaccines available for many of the strains that
lead to meningitis has led to a significant reduction in meningitis incidence in many countries (19, 20). Any reduction in the occurrence of these infections would mitigate
the risk of hearing loss associated with them.
Vaccinations against common bacteria and viruses (e.g. influenza virus) associated with otitis media are also useful in reducing incidence (21–23) (see Box 2.1). It is
important that countries consider these factors when planning for immunization coverage, and that effective immunization policies are implemented in line with
global targets and national priorities.
OTITIS MEDIA: EARLY IDENTIFICATION AND TREATMENT
Early identification and treatment of otitis media will prevent onset, or progression, of hearing loss. Since chronic suppurative otitis media (CSOM) commonly follows
untreated acute otitis media (AOM), efforts should be directed towards the identification and management of AOM in order to prevent its recurrence and avoid chronic ear
infections (7, 25–27). Proper evaluation and management of persons with CSOM and nonsuppurative otitis media (NSOM) through medical and surgical means can prevent
or reverse the auditory effects, while also mitigating the risk of recurrent infections (25, 27). Key considerations when identifying and treating otitis media include:
• Acute otitis media – While the virtues of antibiotic
use versus expectant observation approach are debated, it is important that in places where
complications (such as mastoiditis) are still common and where there is no certainty of proper
follow-up, antibiotics are recommended and made available to ensure effective resolution and to avoid
• Nonsuppurative otitis media or otitis media with effusion (OME) – These can be managed
through the use of antibiotics, grommet insertion and adenoidectomy. The exact intervention must
be determined based on indication and clinical needs (21, 28–32). For this reason, it is important
that persons with NSOM/OME receive care from a suitably qualified practitioner who can manage the
condition or refer to an ear, nose and throat (ENT) specialist.
An ENT surgeon and her team operates on a patient with chronic suppurative otitis media
© James Saunders, Mayflower
SECTION 2 SOLUTIONS ACROSS THE LIFE COURSE: HEARING LOSS CAN BE ADDRESSED 71
• Chronic suppurative otitis media – This must be addressed to ensure: (i) eradication of the
infection responsible for morbidity and mortality associated with CSOM; and (ii) closure of tympanic
membrane perforation, without which hearing loss due to re-infection of the middle ear may present
a constant threat (27). Eradication of infection is possible with proper care through aural toilet with
or without use of local antibiotics or antiseptics (33, 34). Surgical treatment for CSOM is required at
times, either for removal of infection or for surgical repair of the tympanic membrane and middle ear structures. These surgical
procedures, such as mastoidectomy, tympanoplasty and myringoplasty, are well established and highly effective in curing disease and reducing accompanying
hearing loss (21, 35–37). It is important to correctly evaluate every person with CSOM, and that any decision regarding surgical intervention is made in consultation with
an ENT specialist. Information on treatment options for discharging ears, commonin those with CSOM
2.2.3 ADULTHOOD AND OLDER AGE
Although the process of ageing is inevitable, the associated hearing loss cannot be
considered unavoidable. It is now well understood that age-related hearing loss is
a multifactorial condition, of which cochlear/neural ageing is only a part. Hearing
loss is influenced by various determinants such as genetic factors (56), existing ear
conditions, chronic illnesses, and environmental factors such as noise exposure, use
of ototoxic medicines and lifestyle choices. Changes in the modifiable risk factors
can alter the course of a person’s hearing trajectory and influence the extent of
hearing loss experienced in the later years of life (57).
2.2.4 FACTORS FOR HEARING LOSS ACROSS THE LIFE COURSE
LIMITING EXPOSURE TO DAMAGING LEVELS OF SOUND
Exposure to loud sounds has a damaging effect on the cochlear structures that are
so vital for hearing. This risk factor can be mitigated by protecting a person’s ears
against such exposure (58) through:
• Hearing conservation programmes in occupational settings
Hearing conservation programmes can reduce the daily exposure to noise
encountered by workers and limit the impact on the cochlear hair cells and
therefore on their hearing trajectory (59). As depicted in Figure 2.2, occupational
hearing conservation programmes comprise the following: (58–61)
i. Engineering and administrative controls for the reduction of noise levels and
exposure: These include reducing or eliminating the source of noise; changing
materials, processes or workplace layout. Actions may involve purchasing
quieter machinery; the segregation of noise sources; installing panels
or curtains around the sources, and other such measures. Management
policies may involve rotating workers between noisy and non-noisy areas,
and ensuring availability of information and ongoing education in this respect.
ii. Noise monitoring: Monitoring ensures that noise levels and exposure periods
stay within the recommended levels. A level of 85 dBA13 is the maximum
permissible sound level for an 8‑hour time period in occupational settings
(62, 63). If the noise level is higher, the time period needs to be reduced
accordingly (based on a 3 dB exchange rate – see Box 2.3).
iii. The use of hearing protectors: Use includes the provision of devices such as
earmuffs and earplugs, as well as essential training in their correct use. Used
correctly, hearing protectors can significantly attenuate noise reaching the ear.
iv. Education: Key elements of a hearing conservation programme include
education on the effects and control of noise, the impact of hearing loss
and its prevention. Workers, especially those working in noisy areas, should
be taught about hearing, hearing protectors and surveillance. Information
on noise levels, exposure, risk and its mitigation, should also be conveyed
through warning signs, information brochures and notifications.
v. Hearing surveillance: Monitoring the hearing levels of exposed workers should
be conducted through a baseline and regular audiometric evaluation. When
an audiometric shift is detected and validated, it is important that suitable
action to protect the worker from further exposure is initiated immediately. In
addition to regular audiometric evaluation, daily noise exposure monitoring
is effective in promoting safe practices.
Hearing conservation programmes were implemented in many European countries
at the turn of the millennium. France, Italy, the United Kingdom of Great Britain and
Northern Ireland (the United Kingdom), and the Czech Republic have all reported
a decline in the incidence of noise-induced hearing loss (NIHL) in recent years. In
France, the occurrence of physician-reported NIHL dropped by 17% between 2007
and 2012 (64). Improved implementation of such programmes, along with strict
legislation enforcement, can reduce noise levels in workplaces and thereby mitigate
the adverse impact on the hearing trajectory of those exposed (58, 60).
• Safe listening practices in recreational settings
Unlike occupational exposure, people often
voluntarily expose themselves to dangerous levels of sounds while listening
through headphones, stereo systems, in live music events or concerts, nightclubs,
sporting events, the recreational use of firearms and also in fitness classes (66–
68). Safe levels of exposure to leisure noise are described in Box 2.3.
Taking protective measures while enjoying preferred pastimes is an important
factor in affecting a person’s hearing trajectory. Safe listening practices that limit the
amount of sound exposure through personal audio devices (71) and at concerts, for
example through use of earplugs (72), can help to prevent hearing damage occurring
and thereby, potentially maintain hearing capacity over time (66, 67). Specific public
health measures can promote these protective behaviours through, for example:
i. Development and implementation of school-based hearing conservation
programmes: Such programmes educate parents and children and should
be based on the Health Belief Model14 and aim to change the listening
behaviours of young people who are commonly engaged in unsafe listening
(66, 67, 71). Programmes should focus on imparting knowledge of ear hearing,
noise, hearing loss and modifiable risk factors; as well as developing skills for
safe listening, such as use of hearing protectors; use of isolating earphones;
prevention of overexposure through volume reduction (66, 71). At the same
time, the programmes should ensure that earphones or noise protectors do
not interfere with personal safety.
ii. Implementation of the WHO-ITU standard for safe listening devices:
Many users of personal audio devices have listening habits that put them
at risk of hearing loss (70, 71). Research in other areas related to health
suggests that digital platforms, smartphone applications (apps) and mobile
health tools can provide a useful means for improving healthy behaviours and
lifestyles. Although evidence is currently scarce and uncertain, it is unanimous
in acknowledging the potential of such digital platforms to promote healthy
behaviours, especially when they are based on sound behaviour change
theories; are user-friendly; culturally appropriate; accurate; and personalized
(73–78). The use of technology in hearing health and safe listening has not
been studied systematically. Nonetheless, based on findings from other health
areas, there are promising possibilities for using technology – for example
smartphone apps, text messages, computers and the Internet – as a means
for changing listening practices and behaviours (57). To facilitate this, WHO,
in collaboration with the International Telecommunication Union (ITU) and
other stakeholders have made a series of recommendations regarding safe
listening features that should be included in smartphones, MP3 players, ear/
headphones and other devices used for listening (see Box 2.4). This global
standard can be implemented voluntarily by manufacturers of the relevant
devices and also mandated through government policies.
Noise control in entertainment venues
As outlined above, the implementation of noise control legislation in the
workplace has been an important and effective strategy. Although occupational
noise exposure cannot accurately be compared to the voluntary and pleasurable
exposure undertaken as a means for recreation, there are lessons to be learnt
from that field. Policies, regulations and their enforcement can influence a
person’s behaviour, and success through adopting such interventions is evident in
several areas of public health. Examples include the mandatory graphic warnings
on cigarette packages, and ﬁnes imposed for violating seatbelt-wearing laws
(79–82). In view of this, it is believed that the design and implementation of
speciﬁc legislation that regulates sound exposure and management, while also
raising awareness on the risks of loud listening can potentially be effective. It is
anticipated that as regulation becomes more widespread, and the number of
compliant venues increases, it will increase the acceptability of protective hearing
behaviours (83). To this end, WHO is developing an evidence-based “Framework
for control of sound exposure in recreational venues”, with finalization due in
2021. Components of this global framework include:
sound level limits;
measurement of sound;
provision of hearing protection;
dissemination of information and warning messages;
quiet areas; and
sound distribution and management.
EFFECTIVENESS OF NOISE REDUCTION MEASURES
• The adoption and strict implementation of legislation is effective in reducing noise
levels in the workplace, and thereby limits exposure faced by workers and reducing
hearing loss occurrence (60, 64, 85, 86). For example, legislation directed at better
compliance with the law regarding engineering and administrative control in
the mining industry succeeded in reducing noise exposure in underground coal
mines by 27.7% (60).
• The use of properly fitted hearing protection devices is an effective measure,
especially when accompanied by appropriate training in their use (60, 87, 88).
• Limited research has been carried out to date on the effectiveness of programmes
for promoting safe listening among youths; nonetheless, available data reinforces
the importance of health promotion for changing listening behaviours and the
role of technology in doing so.
As indicated in Section 1, some commonly used medicines can seriously impact
the auditory pathway and lead to permanent hearing loss. Prevention of such
ototoxic hearing loss is possible through judicious use of these medicines and
regular auditory monitoring during use, when necessary. Ototoxic hearing loss can
also occur as a result of exposure to chemicals that are commonly encountered in
industries such as printing, construction and manufacturing (see Section 1). Taking
due care with their use, along with hearing surveillance, can mitigate the auditory
risks posed to those exposed.
• Chemical exposure in the workplace
It is possible to prevent the adverse effects of exposure in the workplace through
taking concrete steps, including: (91, 92)
– the initial identification of hazardous materials;
– controlling exposure through substitution, where possible (if not
possible, using engineering controls and administrative measures to
– the use of personal protective equipment, such as chemical-protective
gloves, aprons etc. to reduce dermal exposure;
– the labelling of chemicals that are known to be ototoxic and displaying
warnings clearly; and
– hearing surveillance (further information on noise-related hearing
surveillance is provided in 2.2.4).
• Appropriate use of ototoxic medicines
The risks posed by the unregulated use of ototoxic medicines for hearing
are detailed in Section 1. While in many cases, the use of these medicines
may be necessary and even life-saving, their judicious and regulated use is
essential to ensure that people do not receive them unnecessarily. Wherever
possible, safe and effective non-ototoxic treatment options should be sought
and preferred over those likely to have a lasting negative impact on hearing
(93). Recent developments in the management of drug resistant tuberculosis
(DR-TB) are an example of how this can be achieved. The recently updated
WHO guidelines on DR-TB recommend the use of non-injectables such as
Bedaquiline (94) in the treatment of tuberculosis, to protect against the high
risk of hearing loss associated with the traditionally used injectables (95).
Where ototoxic medicines are essential, particularly in the management of cancer,
tuberculosis, malaria and other diseases, audiological monitoring is crucial to
optimize hearing-related outcomes (93).
Ototoxicity is detected in an individual by regular audiometry to monitor the
auditory response and thresholds, and to determine changes in auditory function
or damage over the course of treatment.
Ototoxicity monitoring assists with:
– comparing the auditory test results during
the course of drug therapy;
– early identification of change in hearing;
– need for potential alterations in therapy;
– prevention of debilitating ototoxic-induced
hearing loss if therapy is changed; and
– auditory rehabilitation to minimize the
negative impact of ototoxicity (93).
EFFECTIVENESS OF OTOTOXICITY PREVENTION MEASURES
• Audiological monitoring undertaken during the use of ototoxic medicines, such as
those used for treatment of multidrug resistant tuberculosis, can help recognize
the early signs of hearing loss. It can provide timely indication and opportunities
for shifting to alternate treatment regimens as a means of conserving the
individual’s hearing capacity (93, 96).
• The adoption and implementation of such protocols by professionals and
governments cannot be considered as optional; given that these are essential in
improving patient outcomes and quality of life, they should form the minimum
standards of care in ototoxicity management (97, 98).