Multiple factors interact to determine the
development of one’s hearing trajectory
across the life course.


An individual’s hearing
trajectory is determined
by the baseline hearing
capacity at birth
along with the diverse
causative and protective
influences experienced
throughout the life
course (3).

During the course of their lifetime, humans are exposed to multiple risk and protective factors
that contribute to their overall hearing capacity (3). The life course model for health development
considers health as an emergent capacity that develops dynamically over time (4, 5). This model
considers health – including hearing – as being affected by multiple factors which range from
genetic and biological to psychosocial and economic (3, 5). Adopting a life-course approach
allows the preservation of hearing to be viewed as an important goal, and hearing loss not as a single
event or occurrence, but as an outcome of factors experienced from the prenatal period through childhood and adulthood (3, 6)
and into older age.4 This provides opportunities for intervention, in the form of
prevention, identification, treatment and rehabilitation, across the life course,
Hearing throughout a person’s life can be visualized in the form of a trajectory (the
hearing trajectory), the course of which determines our hearing capacity at any
point in time. An individual’s hearing trajectory depends on the baseline capacity at
birth, and the multiple risk or preventive factors encountered during the life course
(3, 6), as described in Figure 1.1. The mechanism by which hearing occurs in the ear
is illustrated in Figure 1.2.


It is evident that many determining factors of the hearing capacity – genetic,
biological, psychosocial and environmental – experienced at different stages of life,
influence the ears and can either lead to hearing loss or protect against it. Many
ear conditions, such as otitis media, are treatable, and many causes of hearing loss
– nutrition, ear hygiene and loud noise, for example – can be avoided by taking
preventive actions at a personal level. Both causative and preventive factors interplay
to determine the occurrence, nature, severity and progression of hearing loss, thus
the hearing capacity of an individual is determined by: (3)
1. Baseline hearing capacity at birth.
2. Exposure to, or presence of, causative factors (genetic, biological, behavioral
or environmental).
3. Protective actions mitigating the risk factors.
Although these factors can be encountered at different periods across the life span,
individuals are most susceptible to their effects during critical periods in life, such as
before birth or in the first years of life – a period of physiological development and

SECTION 1 THE IMPORTANCE OF HEARING ACROSS THE LIFE-COURSESounds travel through the outer part of the ear to strike and set into vibration the tympanic membrane (eardrum). These vibrations are transmitted through the three ossicles (bones) in the middle ear to the cochlea in the inner ear. The outer and middle ears serve to amplify the sound vibrations setting into motion the fluid contained within the cochlea. This movement is transduced by hair (sensory) cells within the cochlea to an electrical, nervous impulse that is transmitted by the auditory nerve to the brain where it is perceived as sound (7).

maturation for the hearing system and critical for
language acquisition (3). The impact of risk factors for
hearing loss is also higher in older age groups when
neurogenerative changes set in. However, the decline
in hearing experienced at this age is not a simple,
inevitable, degenerative process associated with
growing old: it is the outcome of genetic influences,
health conditions, lifestyle and environmental
experiences that are embedded in the physiological
system of hearing (6) and have influenced it during
the course of life.

Certain health conditions or environmental influences
are more likely to be experienced at specific stages of
the life course; these are detailed in the time period
they are considered most relevant (Table 1.1). Factors
that may be encountered at any point, or equally, at all stages of life are listed
in Table 1.2 (3, 8–10).
In addition to the information provided in the tables, three specific factors that can
lead to hearing loss are highlighted: otitis media; exposure to loud noise; and age-related
hearing loss. These are considered especially relevant from a public health
perspective, mostly due to their high prevalence in the community or their well-established
preventive and therapeutic mechanisms.


Otitis media (34–40)
The term “otitis media” (OM) reflects a range of conditions, all characterized by
inflammation of the middle ear. Although anyone of any age can develop otitis
media, children are most commonly affected. The different forms of OM include:
• Suppurative otitis media (infective conditions):
– Acute suppurative otitis media (AOM), including recurrent acute otitis media
– Chronic suppurative otitis media (CSOM)
• Nonsuppurative otitis media (NSOM) including acute and chronic NSOM. NSOM
is synonymous with otitis media with effusion (OME)
Acute otitis media (AOM) is a middle ear effusion accompanied by acute infection.
Such an infection can result in a perforation of the tympanic membrane, with the
possible development of chronic suppurative otitis media (CSOM). Incomplete
resolution of AOM is often followed by a period with nonsuppurative otitis media
(NSOM). At the same time, chronic NSOM may itself be a risk factor for AOM. Hence
all conditions are interrelated and an individual with otitis media may experience
its different forms at different times based on a variety of influences .



Various factors and interventions can either prevent or address the above-mentioned
causes and thereby prevent onset of hearing loss or delay its progression. Detailed
information on ear and hearing care (EHC) practices that can prevent ear diseases
and maintain hearing capacity is provided below. The most relevant preventive actions
that can be undertaken by individuals at a personal level across the life course to
maintain their own hearing capacity is set out in Table 1.2 (122–124). Preventive public
health actions, not included in the table, are described in Section 2 of this report.

Practicing good ear hygiene

Practicing good ear hygiene can prevent many of the common conditions associated
with hearing loss, as well as leading to early identification so that hearing loss can
be prevented or reversed. Simple measures of ear hygiene include:
• Avoiding the use of cotton buds (68, 143). It is important for people to
understand that cleaning the inside of their ears is not usually necessary, and
that wax is a normal ear secretion and harmless in most people (70, 71). The
common habit of cleaning the ears excessively with use of cotton-tipped buds
irritates the skin of the ear canal, which may lead to infection, and even increase
the chances of wax impaction (71).
• Not inserting or instilling any objects
or liquids into the ear. Unless their use is
specifically recommended by a health-care
practitioner objects or liquids should not be
inserted into the ear. Different types of oils
are commonly used; and foreign bodies such
as cotton-tipped buds, matchsticks, feathers,
pins, or pencils introduced to clean the inside
of the ears are sometimes left in the ear canal
causing further infection or harm (70, 71).
Their use can result in trauma to the ear canal,
perforations of the ear drum and may aggravate
cerumen impaction.
• Not using home remedies. The use of home
remedies for common ear conditions (such as
ear pain) is widespread and can cause harm
rather give benefits (144). Remedies such as ear
candling (71, 145), plant juice/hot oil instillation
should not be used to treat ear diseases or
conditions, nor should seeking care from
untrained providers as is common practice in
some parts of the world (146).
• Seeking prompt medical attention. Seeking
timely medical care for the treatment of common colds, ear pain, ear fullness, ear
discharge, bleeding from the ear, or hearing loss, can help prevent or identify ear
and hearing problems. These symptoms can indicate an underlying ear disease
such as otitis media and commonly require a medical evaluation for diagnosis
and management (71). While ear fullness, pain and slight hearing loss may be
due to cerumen impaction, it cannot be presumed to be the cause, and needs
confirmation by a trained health-care provider.

Avoiding loud sounds and loud noise

As noted in this section, the recommended level of sound exposure is below 80 dB
for a maximum of 40 hours per week. Indications of noise being too loud is when,
for example, voices need to be raised in order for conversation to be understood;
when it is difficult for the listener to understand what a person is saying when at
an arm’s length distance; or when listeners develop pain or a ringing sensation in
their ear(s). Hearing can be protected through adopting simple measures, such as:
• Keeping noise volumes down
Sound exposure can be reduced when listening to personal audio devices by:
– Keeping the volume of the personal audio devices (smartphones or MP3
players that are used with headphones/earphones) below 80 dB. This can
be checked with the use of certain freely available smartphone applications
(apps). Some devices provide this as an inbuilt feature. In the absence of
these, the rule of the thumb for staying safe is to listen at a volume below
60% of maximum.
– Using carefully-fitted and, where possible, noise cancellation earphones or
headphones. Well fitted earphones and headphones allow music to be heard
clearly at lower levels of volume. In addition noise-cancelling earphones and
headphones cut down the background noise, so that users can hear sounds
at lower volumes than otherwise needed. For example, frequent users of
personal audio devices on trains or airplanes should consider using noisecancelling
earphones or headphones in these settings.
• Protecting ears in noisy situations
In noisy workplaces and when frequenting nightclubs, discotheques, bars,
sporting events and other noisy places, sound exposure can be limited by:
– Regularly using earplugs as hearing protection. Well-inserted earplugs
can help to reduce the level of exposure considerably. If inserted correctly,
earplugs can reduce the exposure by 5–45 dB, depending on the type.
– Maintaining a distance from the sources of sound, such as loudspeakers,
can reduce the amount of sound energy a person is exposed to.

• Minimizing the time spent in noisy environments
It is especially important to control the sound exposure for individuals who
encounter loud sounds on a regular basis at their place of recreation or work.
This can be achieved by:
– Limiting time spent listening using personal audio devices. In addition, when
listening to the devices, keeping the volume low, as indicated above.
– Taking short breaks away from loud sounds. When in a noisy environment,
trying to take regular breaks and moving to a quieter area. This could help
the sensory cells to recover from the fatigue caused by noise exposure and
reduce the risk of hearing loss.
• Monitoring personal sound exposure
Knowing the level of sound being experienced can help a person set their own
limits according to their own preference. This can be achieved by:
– Using smartphone apps that monitor personal sound exposure. Apps are
available that can help one to monitor exposure through the device and also
in the external environment.
– Using smartphones, currently available, that include inbuilt safe listening
features. Use of these can assist people in making safe listening choices.