Hearing and Prevalence of hearing loss
Your ear consists of three major areas: the outer ear, middle ear, and inner ear. Sound waves pass through the outer ear and cause vibrations at the eardrum. The eardrum and three small bones of the middle ear amplify the vibrations as they travel to the inner ear. There, the vibrations pass through fluid in a snail-shaped structure in the inner ear (cochlea).
Attached to nerve cells in the cochlea are thousands of tiny hairs that help translate sound vibrations into electrical signals that are transmitted to your brain. Your brain turns these signals into sound.
Hearing loss is the condition that results when any part of your ear isn’t working the way it should. Hearing loss refers to a partial or total inability to hear. It can result from problems with the ear (outer, middle, and/or inner), the vestibulocochlear nerve (i.e., cranial nerve eight or CN VIII), and/or the auditory system. Hearing loss refers to an audiologic diagnosis of hearing thresholds outside the range of typical hearing.
Despite India’s improving health indices, hearing disability remains persistently high. It is a major contributor to the loss of personal potential and a financial strain for the individual and the country. A large-scale multicentric study to identify the degree and type of HL, social awareness campaigns, widespread neonatal screening, strengthening treatment facilities, and well-funded rehabilitation programs can counter the rising prevalence of hearing impairment.
The 2002 National Sample Survey (NSS) found HL to be the second most common cause of disability and top cause of sensory deficit; 291 per 100 000 persons surveyed had HL, which included mainly profound (32%) and severe HL (39%).7 The 2011 Indian Census noted that 2.21% of the Indian population was afflicted with some disability. The three most common were locomotor (20%), vision (19%) and hearing (19%).8 The 75th National Sample Survey (NSS) (2017–2018) report, defined hearing disability as a difficulty in hearing day-to-day conversational speech but excluded unilateral hearing impairment. Hearing disability was estimated in 0.3% of the population. About 49.8% of them reported hearing only loud sounds or inability to hear at all.
In 2018, the WHO estimated that the global burden of DHL was 466 million (6.12% of the world’s population). One-third of the population above 65 years of age was suffering from DHL. The number of DHL patients is predicted to be 630 million by 2030 and 900 million by 2050.