ASOURCE Navi

Recent research has revealed that age-related hearing loss is the most important "modifiable factor" in the development of dementia, and early use of hearing aids as a preventative measure is gaining attention. Although hearing loss is present in approximately 70% of people aged 75 and over, many people simply assume it's "due to age" and do not take appropriate measures. However, hearing and cognitive function are closely related, and it has become clear that hearing loss increases the risk of dementia. This series will explain the importance of hearing aids in two parts. In the first part, we will explore in detail the impact of age-related hearing loss on cognitive function and the mechanism by which it increases the risk of dementia.

Have you ever experienced something like, "The volume on the TV has gotten louder recently," or "My family says I have to ask for repeats too often"? Many elderly people simply dismiss these symptoms as "just because of age," but in fact, there are hidden health risks that should not be overlooked.

A report by the Lancet International Commission, published in the medical journal The Lancet in 2024, shocked the medical community by revealing that hearing loss is the biggest "modifiable risk factor" for developing dementia among people aged 18 to 65. "Modifiable factors" here refer to risk factors that can be addressed through lifestyle improvements, etc.
Research has calculated that hearing loss contributes to the risk of dementia by 7%, which is equivalent to high LDL cholesterol (7%) and significantly higher than other lifestyle-related diseases such as high blood pressure (2%), diabetes (2%), smoking (2%), and obesity (1%). Of particular note is that it is estimated that approximately 70% of people aged 75 and over suffer from age-related hearing loss, indicating an extremely large social impact even considering the population size.
The international report concluded that eliminating all 14 risk factors, including hearing loss, could potentially prevent up to 45% of dementia cases.

There are three main mechanisms thought to explain why and how hearing loss increases the risk of dementia.
The first is "social isolation." When hearing becomes difficult, it becomes difficult to understand the content of conversations. People gradually begin to avoid interacting with others because they feel embarrassed to ask for clarification or don't want to bother those around them. Reducing participation in gatherings and refraining from going out altogether reduces stimulation to the brain, which could lead to a decline in cognitive function.
The second is "increased cognitive load." People with hearing loss use a significant amount of their brain's processing power (cognitive resources) to understand conversations. Constantly straining their brains by trying to "listen" depletes brain resources that should otherwise be used for memory and thinking.
The third is "structural changes in the brain." When auditory stimulation is reduced over a long period of time, the auditory cortex of the brain begins to atrophy. Furthermore, brain imaging studies suggest that this change may promote overall brain atrophy and degeneration of neural circuits.

Our hearing ability peaks in our 20s and then gradually declines. One of the most notable characteristics of age-related hearing loss is the difficulty in hearing high-frequency sounds. Consonants such as the "sa" and "ta" sounds used in everyday conversation belong to a relatively high frequency range, so if it becomes difficult to hear these sounds, it becomes difficult to understand the entire speech.
For example, "sashisuseso" sounds like "ashiaseo," and it becomes difficult to distinguish between "kakakikukeko" and "tachitsuteto." As a result, people may mistakenly think, "Maybe he can't see," even though he actually means "I can't hear the story," not "I can't see the story."
It is important to note that this change occurs very gradually, so it is difficult for the individual to notice. In many cases, the individual first becomes aware of this change when family members or people around them point out that the individual has been asking for repeats more often recently.

Have you noticed any changes in your hearing? For example, have you recently been turning up the volume on the TV or radio, or have you had trouble hearing conversations in noisy places? Also, have you had trouble hearing and understanding phone conversations, or have your family members started to point out that you keep asking the same thing over and over again? If these situations continue, you may find that talking to people in general becomes a chore.
If you notice these changes, you may be experiencing a decline in hearing due to aging or other factors, commonly known as hearing loss. Recently, there are online tools available to check your hearing, so you can easily self-check your hearing at home. These tools can be useful as a starting point for becoming aware of the state of your hearing, but they are only a guideline. To receive an accurate diagnosis and appropriate treatment, it is important to undergo a professional hearing test at an otolaryngologist.

If you notice a change in your hearing, it's important to take action early. Taking appropriate measures, such as using hearing aids, can not only improve your hearing but may also reduce your risk of dementia. According to a study that analyzed only participants at high risk of dementia, the group that used hearing aids reported that cognitive decline after three years was reduced by approximately 50% compared to the control group that did not use hearing aids.

Don't just give up and think, "It's just because I'm getting older." If you notice any changes in your hearing, taking action early may be the first step in preventing dementia. Why not take another look at your own and your family's hearing?