Presbycusis

What is Presbycusis?

Presbycusis is the medical term for age-related hearing loss. It is a common condition that gradually affects individuals as they get older, typically beginning in their 60s. This form of hearing loss mainly affects the ability to hear high-pitched sounds such as birds chirping or children's voices. It also makes it harder to hear consonants in speech, which makes speech comprehension more challenging especially in noisy environments.

The condition is progressive, meaning it worsens over time, and it affects both ears equally. While presbycusis is a natural part of aging, it can significantly impact the quality of life, making it important to recognize and address early.

Presbycusis and Dementia: The Connection

Research has shown a strong link between hearing loss and cognitive decline, including dementia. According to a landmark study published in The Lancet, hearing loss is one of the most significant modifiable risk factors for dementia, accounting for up to 8% of the total risk. The exact mechanism isn’t fully understood, but theories include increased cognitive load (where the brain has to work harder to process sounds), social isolation due to communication difficulties, and changes in brain structure related to auditory processing. Addressing hearing loss with devices like hearing aids or cochlear implants may help reduce this risk, although more research is needed to confirm these benefits.

The Prevalence of Presbycusis in Canada

In Canada, presbycusis affects a significant portion of the elderly population. According to the Canadian Hearing Society, approximately 47% of Canadians aged 60 to 79 experience some degree of hearing loss, with presbycusis being the most common cause (Canadian Hearing Society, 2021). By the age of 70, nearly 70% of individuals have measurable hearing impairment. Globally, hearing loss is the third most common chronic condition among the elderly.

Given these statistics, it's clear that presbycusis is a widespread issue that requires attention and management to ensure the well-being of the aging population.

Different Types of Presbycusis

Presbycusis can be categorized into four main types, based on what part of the auditory system is affected. Each type can contribute differently to hearing difficulties, and most individuals will experience a combination of these changes:

1. Sensory Presbycusis: This type involves the degeneration of sensory cells in the cochlea, which are responsible for converting sound waves into nerve signals. This forms mainly leads to a loss hearing in the high-frequencies (high pitch sounds), but the clarity of the sound is maintained (speech understanding). This form is best suited for hearing aids.
   
   

2. Neural Presbycusis: Here, the auditory nerve fibers that transmit signals from the cochlea to the brain deteriorate, causing primarily difficulties in speech understanding (the clarity of the sound). There is also hearing loss in the high frequencies, but to a lesser extent. This type of presbycusis makes speech understanding difficult in noisy environments. While it remains possible to get hearing aids with this type, they may not be as beneficial. 
   
   

3. Metabolic or Strial Presbycusis: This form is characterized by degenerative changes in the a specific part of the cochlea called the "stria vascularis", a structure that helps maintain the ear's chemical balance necessary for sound processing. This type affects the overall sensitivity of hearing across all sounds (low to high frequencies, "flat" hearing loss). 
   
   

4. Mechanical (or Cochlear Conductive) Presbycusis: This type involves stiffening of a structure in the cochlea called "basilar membrane", which affects how sound vibrations are transmitted to the hair cells. This alters its mechanical properties and also leads to a broad loss of hearing sensitivity, but mainly affecting the base of the cochlea and the high frequencies. 

 

What is "Normal" Aging of the Ear?

While hearing decline is a normal part of aging, there are standards for what is considered “normal” hearing loss. The International Organization for Standardization (ISO) has established norms based on age groups and gender. The most recent age-related hearing loss standards are called ISO 7029 (published in 2017). This standard is useful for estimating the amount of hearing loss in a specific group and for comparing an individual’s hearing loss in relation to the "normal" aging of the ear. For example, a person in their 60s might typically lose about 25 to 40 decibels (dB) of hearing at higher frequencies (4,000 Hz and above). This gradual decline is considered part of healthy aging and doesn’t necessarily mean the person has presbycusis that requires intervention. However, not all hearing loss is due to aging; it is crucial to distinguish between normal aging and other potential ear conditions.

Is There a Genetic Predisposition to Presbycusis?

Genetics play a significant role in determining who is more likely to develop presbycusis. Studies suggest that up to 35-55% of age-related hearing loss cases may have a hereditary component. Specific genes, such as those involved in cochlear function and repair, have been linked to presbycusis. In 2019, I contributed to research on the genetic causes of presbycusis, highlighting advancements in our understanding (Tawfik et al., J Neurosci Res, 2020). My mentor, Dr. Rick Friedman from the University of California - San Diego, dedicated much of his career to elucidating these processes. A large 2021 study published in Nature Communications identified several genetic variants associated with susceptibility to age-related hearing loss. Together, these studies emphasize the importance of family history when assessing risk in individuals suffering of hearing loss. 

 

Other Factors Contributing to Presbycusis

While aging and genetics are the primary causes of presbycusis, several "external" factors can contribute to its development:.

• Noise Exposure: Prolonged exposure to loud noises can accelerate hearing loss. This includes work-related noise, recreational activities, and even environmental noise pollution (See noise-induced deafness).
  
  

• Health Conditions: Researchers have been linking hearing loss to health conditions such as diabetes, hypertension, and cardiovascular diseases. These conditions can impair cochlear microcirculation, leading to damage in the stria vascularis and hair cells, thereby increasing the risk of hearing impairment (Adamu et al., 2024). Longitudinal studies suggest that hypertension and cardiovascular risk scores are strongly associated with faster hearing decline, particularly in older adults (Frank, 2023). Another study highlights that individuals with two or more major cardiovascular risk factors, such as high blood pressure, diabetes, or smoking, are significantly more likely to develop hearing loss (Baiduc et al., 2023). Cardiovascular conditions may exacerbate hearing decline due to mechanisms like oxidative stress and inflammation. These findings suggest that addressing cardiovascular health through lifestyle modifications and risk management could mitigate hearing loss progression. However, more studies are needed to clearly define these risks.
  
  

• Ototoxic Medications: Certain medications (chemotherapy agents and certain antibiotics) have side effects that can damage the inner ear (see Ototoxicity).
  
  

• Smoking: Research has shown a significant link between smoking and hearing loss, with both active and passive smoking posing risks. Smokers are more likely to experience hearing impairment, particularly at higher frequencies, due to vascular and oxidative stress affecting the inner ear. One study found that smokers had a 40% prevalence of hearing loss compared to 10% in non-smokers (Meghani et al., 2024. Passive smoking also significantly elevates the risk, with exposed individuals—especially children—showing up to four times higher odds of developing sensorineural hearing loss. Noise-exposed workers who smoked, or were passively exposed to smoke, had higher hearing thresholds, highlighting a compounded risk when smoking and noise exposure intersect. The severity of hearing loss correlates with smoking intensity, underscoring the importance of cessation programs. Public health interventions are crucial to mitigate these risks and protect vulnerable populations.
  
  

• Diet and Exercise: Studies exploring the impact of diet and exercise on hearing health suggest these factors play significant roles in mitigating the risk of hearing loss. Diets rich in antioxidants and anti-inflammatory nutrients, such as those found in Mediterranean-style eating patterns, have been shown to protect against audio-vestibular dysfunction, including hearing loss, by reducing oxidative stress and inflammation. Additionally, diets with reduced sugar and fat content may lower the risk of inflammation-related hearing loss, as excess carbohydrate and lipid intake have been correlated with worse auditory function (Chen et al., 2022). Physical exercise has also been linked to improved auditory outcomes through its positive effects on cardiovascular health, which supports adequate blood flow to the cochlea (Chalke et al., 2023). This evidence highlights the importance of a balanced diet and regular exercise in maintaining hearing health and delaying age-related auditory decline.

How is Presbycusis Evaluated?

Diagnosing presbycusis involves both medical and audiological evaluations. The process typically includes:

• Medical evaluation: An ENT specialist will start by taking a detailed medical history and conducting a physical examination of the ears to rule out other causes of hearing loss.
  
  

• Audiological testing: A hearing test (audiogram) measures hearing ability at different frequencies. High-frequency hearing loss is a hallmark of presbycusis. Other tests, like tympanometry, may assess middle ear function
  
  

• Speech Audiometry: This test evaluates the ability to understand speech at different volume levels and in various noise environments. 

  This is an essential part of the audiological evaluation for presbycusis, as it aids in identifying the specific type of presbycusis you may have and assists your clinician in recommending appropriate interventions, such as hearing aids or more advanced treatments like cochlear implants.

 

Managing and Treating Presbycusis

While presbycusis cannot be cured or reversed, several treatment options can help manage the condition and improve quality of life.

Since hearing loss has been identified as a reversible factor contributing to cognitive decline and dementia, it is highly recommended to address presbycusis promptly and with seriousness.

1. Hearing Aids: These devices amplify sounds, making it easier to hear and understand speech. Modern hearing aids come with advanced features like noise reduction and connectivity to smartphones.
   
   

2. Assistive Listening Devices: These include devices like amplified telephones and TV listening systems that help improve hearing in specific situations.
   
   

3. Communication Strategies: Learning lip-reading, using visual cues, and adopting clear communication practices can also help.
   
   

4. Regular Monitoring: Regular check-ups with an audiologist are crucial to monitor the progression of hearing loss and adjust treatment plans accordingly.
   
   

5. Cochlear Implants: For severe cases of hearing loss, cochlear implants may be an option. These devices bypass damaged parts of the ear and directly stimulate the auditory nerve.

Final Thoughts

Presbycusis is a common and natural part of aging, but it doesn’t have to diminish your quality of life. Early evaluation and treatment can make a big difference. If you or someone you know is experiencing hearing difficulties, consult an ENT specialist or audiologist to explore the best options for maintaining hearing health.