Last updated on Apr 25, 2018
Over time, researchers have noticed a positive correlation between early Alzheimer’s disease and hearing loss. A recent longitudinal study at Johns Hopkins suggests that for those over 60, over one-third of the risk of developing dementia (including Alzheimer’s) could be attributable to hearing loss.
To fully understand how hearing loss and Alzheimer’s are related, it’s necessary to take a look at each individually. Hearing loss, which the World Health Organization defines as not being able to hear sounds of 25 decibels or less in the speech frequencies, affects 48 million people in the United States, or one out of seven people. This number jumps to one out of every three people once you hit age 65.
Hearing loss especially affects veterans (60% of returning military service members experience hearing loss), and men are more likely to experience hearing loss than women. As people age, they become more likely to experience hearing loss.
Alzheimer ‘s disease, meanwhile, is a form of dementia that disrupts memory, thinking, cognition, and behavior. Symptoms develop slowly and gradually worsen. Alzheimer’s is by far the most common type of dementia (accounting for 60-80% of all cases), and it affects more than five million Americans.
Hearing loss and Alzheimer’s share many overlapping symptoms. Those suffering from hearing loss or Alzheimer’s may also experience depression, anxiety, and increased paranoia. They may respond inappropriately to social cues or feel isolated. They typically experience problems following conversation and understanding what is being said, and they score lower on mental function tests. They are often in denial, acting defensive, and showing negative feelings.
Much of this correlation can be traced to how brain activity and hearing operate. The temporal cortex, occipital cortex, posterior parietal cortex, and brain stem all contribute to our ability to hear a sound and judge its location, and they’re very close to the area
of the brain that Alzheimer’s first damages.
When we hear, the sound travels into the ear and stimulates small sensory hair cells in the cochlea (the inner ear), whose vibrations trigger electrical impulses to move along nerves to the brain stem. Once in the brain stem, the electrical impulses travel to the temporal lobe, which is located just above the ear.
Researchers have also found that mild hearing loss doubles the risk of dementia, and that risk rises as hearing loss increases. The connection between hearing loss and brain activity can be traced back to the hair cells in the cochlea. Cochlear hair cells can be damaged as a results of age or exposure to loud noises for a long period of time (as in the case of war veterans), and the fewer hair cells there are, the harder it is to capture a sound.
An active, healthy brain is a great defense against the symptoms of both hearing loss and Alzheimer’s disease.
Whether you or a loved one are concerned hearing loss or dementia, a good first step is to talk to your doctor about testing for hearing loss. By getting treatment for hearing loss early, you can address many of the symptoms of both hearing loss and Alzheimer’s while maintaining high cognitive function. Many studies have shown that getting fitted with hearing aids greatly improves Alzheimer’s patients’ ability to understand and communicate, prolonging a higher quality of life.