Age-related hearing loss

Age-related hearing loss (also known as presbycusis) is a decrease in hearing ability that happens with age. In most cases, the hearing loss affects both ears. It can begin as early as a person’s thirties or forties and worsens gradually over time.

Age-related hearing loss first affects the ability to hear high-frequency sounds, such as speech. Affected people find it increasingly difficult to understand what others are saying, particularly when there is background noise . However, because the hearing loss is gradual, many people do not realize they cannot hear as well as they used to. They may turn up the television volume or start speaking louder without being aware of it.

Age-related hearing loss is one of the most common health conditions affecting older adults. Tens of millions of people worldwide are affected. In the United States, an estimated one-third of people over age 65, and half of those over 85, have some hearing loss.

The causes of age-related hearing loss are complex. This condition results from a combination of genetic, environmental, and lifestyle factors, many of which have not been identified. Age-related hearing loss is most commonly associated with changes in the inner ear, where sound waves are converted to nerve impulses that are sent to the brain. 

Age-related hearing loss typically does not have a clear pattern of inheritance, although many affected individuals report a family history of the condition. Studies suggest that people who have close relatives with severe age-related hearing loss have an increased risk of developing severe hearing loss themselves as they age. However, it can be difficult to tell whether age-related hearing loss is inherited in a family because the condition is so common in the general population.

Nonsyndromic hearing loss

Nonsyndromic hearing loss is a partial or total loss of hearing that is not associated with other signs and symptoms. In contrast, syndromic hearing loss occurs with signs and symptoms affecting other parts of the body.

Nonsyndromic hearing loss can be classified in several different ways. One common way is by the condition’s pattern of inheritance: autosomal dominant (DFNA), autosomal recessive (DFNB), X-linked (DFNX), or mitochondrial (which does not have a special designation).

Between 2 and 3 per 1,000 children in the United States are born with detectable hearing loss in one or both ears. The prevalence of hearing loss increases with age; the condition affects 1 in 8 people in the United States age 12 and older, or about 30 million people. By age 85, more than half of all people experience hearing loss

The causes of nonsyndromic hearing loss are complex. Researchers have identified more than 90 genes that, when altered, are associated with nonsyndromic hearing loss. Many of these genes are involved in the development and function of the inner ear. Mutations in these genes contribute to hearing loss by interfering with critical steps in processing sound. Different mutations in the same gene can be associated with different types of hearing loss, and some genes are associated with both syndromic and nonsyndromic forms.

As discussed above, nonsyndromic hearing loss has different patterns of inheritance. Between 75 and 80 percent of cases are inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Usually, each parent of an individual with autosomal recessive hearing loss carries one copy of the mutated gene but does not have hearing loss.