• Each individual has a unique hearing trajectory that is shaped by diverse
    influences experienced throughout the life course; these include genetic
    characteristics, and biological, behavioural and environmental factors.
  •  The course of the hearing trajectory determines a person’s hearing capacity
    at any point during their life. Causative and protective factors influence
    hearing capacity.
  • Although factors influencing hearing capacity can be encountered at
    different periods of a person’s life, some factors are more likely to be
    experienced – or individuals may be most susceptible to their effects – at
    specific points in life.
  • Section 1 describes the causative and protective influences encountered
    during the prenatal period through to older age, with emphasis placed on
    those most relevant to public health.
  • Hearing capacity is commonly measured using pure tone audiometry
    and classified based on the audiometric hearing thresholds. Any decline
    in hearing capacity is referred to as hearing loss or hearing impairment2
    which may range in severity from mild to complete.
  • Globally more than 1.5 billion people experience some degree of hearing
    loss. Of these, an estimated 430 million have hearing loss of moderate or
    higher severity in the better hearing ear. Prevalence of hearing loss varies
    across WHO regions; the vast majority of people affected live in low- and
    middle-income countries of the world.
  • The impact of hearing loss on a person is determined not only by the
    severity and profile of the loss, but also largely on whether the hearing
    loss is addressed by effective clinical or rehabilitative interventions, and
    the extent to which the environment is responsive to the person’s needs.
  • If unaddressed, hearing loss can negatively impact many aspects of life:
    communication; the development of language and speech in children;
    cognition; education; employment; mental health; and interpersonal
    relationships. Hearing loss can cause low self-esteem, is often associated
    with stigma, and can significantly impact the families and communication
    partners of those living with the condition.
  • Globally, unaddressed hearing loss poses an annual cost of over $ 980 billion.3
    This includes costs related to health care, education, productivity losses,
    and societal costs. Many of these costs can be mitigated through the use
    of cost–effective interventions, as described later in the report.
  • Hearing is a key component of human intrinsic capacity; it is the sense most relied
    upon to communicate and engage with others. Any decline in hearing capacity at
    any point during the life course, if not addressed in a timely manner, can adversely
    affect day-to-day functioning (1, 2). Section 1 highlights these factors and explores
    the impact of unaddressed hearing loss on those affected, their families and society
    as a whole.