The association between neurocognitive disorders such as dementia and hearing loss has been recognised for many years. In published longitudinal studies, hearing loss has been consistently associated with a risk of developing dementia of about 50 percent greater than expected. For example, less input from sensory organs may decrease cognitive function. In addition, the language heard may be degraded to the point that it is difficult to understand what is being said regardless of the ability to hear the other person talk, and this can lead to cognition decline. Finally, there may be an intervening problem that affects both hearing and cognition, such as cardiovascular disease. Sadly, given the potential extent of the problem, these mechanisms have not been clearly established and much more research is required to determine the pathway from hearing loss to cognitive decline. Yet, as noted above, the association is clear.
Evidence is accumulating that the use of techniques and therapies to improve hearing may reduce the decline in cognition caused by hearing loss. In more than one study, the use of hearing aids has been independently associated with improved cognition, even when social isolation and loneliness were taken into account. These results are promising, but more evidence is needed. A large study is currently underway to test whether hearing aids can improve cognition. If so, we have yet another reason to encourage the use hearing aids especially among older adults. The value of therapy from an audiologist should also be considered. In more serious conditions, cochlear implants may be of benefit.
Depression is another psychiatric problem that has been demonstrated, as noted above, to be associated with hearing loss. As with cognitive impairment, reduced activation of neural pathways, in this case, auditory pathways, may disrupt critical brain communications, which are essential for maintaining mood. Cognitive reserve and executive function may be compromised and thus contribute to depression.
The depressed may benefit from traditional therapies, such as antidepressants and talk therapy. Nevertheless, if the hearing impairment cannot be improved, these therapies encounter a barrier that is difficult to overturn. A sympathetic audiologist or hearing instrument specialist could lead to benefits, not the least of which may be better compliance with using hearing aids. For this reason, these specialists should be well versed in identifying and providing support for the depressed with hearing disorders.
Hearing loss has been thought to be associated with psychoses for decades. More recent studies have associated hearing loss with a variety of psychotic symptoms, including hallucinations, delusions, and delirium. Auditory hallucinations are especially frequent, perhaps in one-third of people with hearing impairment. These symptoms may range from simple buzzing to music and voices. Yet given that the hearing impaired may experience tinnitus or may have difficulty distinguishing external sounds, we must not be too quick to identify some of these symptoms with a psychotic disorder. Biological mechanisms, such as greater sensitivity to amphetamines, which overstimulate portions of the brain, can produce psychotic symptoms. Antipsychotic medications should be administered to these individuals if these drugs are proven to not have side effects that impact hearing function. These drugs have proven to be relatively safe and effective.
In summary, both hearing health and mental health care specialists should recognise the association between hearing loss and psychiatric disorders. This is especially true since these disorders can be treated