Hearing and memory loss have long been considered inescapable side effects of aging, but could hearing loss actually predict Alzheimer’s Disease and dementia?
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, if a causal link could be found.
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 – a number that jumps to one out of every three people once you hit age 65. Hearing loss especially affects veterans of the war in Iraq and Afghanistan (60% of these veterans experience hearing loss upon return), 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 feel depression, anxiety, and an increased paranoia. They may respond inappropriately to social cues or feel isolated. They typically experience problems talking or 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 back 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 also 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 dementia risk, and the risk of dementia rises as hearing loss also rises. The specific 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 less 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 about either symptoms of hearing loss or dementia, a good first step is to talk to your doctor about getting tested 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 improve Alzheimer’s patients’ ability to understand and communicate, prolonging a higher quality of life.