Is hearing loss related to dementia?

For the audiologist who fits older adults with hearing aids, the task of parsing out communication deficit related to the hearing loss itself versus unrelated issues of aging is a formidable challenge. It is not uncommon for a patient to enter the office several times with relatives complaining that the hearing aids are no longer assisting with communication benefit.  The likely assumption is that the hearing aids are not functioning properly, or the hearing loss has changed. In cases where neither of these are evident, it can be difficult to localize the problem. in a number of cases it is eventually discovered that the patient has developed a neurodegenerative condition such as Alzheimer’s or Parkinson’s, or even that a mini-stroke has occurred without the patient’s or family’s knowledge.  Audiologists have intensive medical training to recognize behavioral and physiologic signs of this type of pathology and recommend referrals to appropriate professionals to diagnose and treat the true condition. 

Emerging research presents evidence that a distinct relationship exists between presbycusis, or hearing loss related to aging effects, and dementia (Lin, et. al., 2012). The ears receive and analyze sounds, but understanding and interpretation of the sounds occurs in specialized sensory areas of the brain. The effects of sensory deprivation, especially of the auditory nature, has far-reaching and global impact on cortical function. The lack of input and stimulation to those neural regions causes the brain to reorganize the way it processes all sensory information (Peele, et. al. 2011). The exact nature of this mechanism is yet unknown, however, it is apparent that maintaining auditory stimulation via hearing aids or cochlear implants may play a role in delaying the onset of neurodegenerative dementia. 

The prevalence of mental health symptoms in those with untreated hearing loss is alarmingly high. Several studies have shown hearing loss to be strongly associated with anxiety, depression, general distress, and post-traumatic stress (Hallam, et. al., 2006; Gopinath, et. al., 2009).  Cochlear implantation in the older adult is becoming more commonplace as an intervention for acquired hearing loss and is well documented in its beneficial impact on speech perception, depression, and quality of life in this population (Francis, et. al., 2008; Poissant, et. al., 2002).  It  is logical to presume that even hearing aid stimulation could possibly provide a similar beneficial effect. 

According to Lin, et. al., (2012), those with moderate hearing loss are three times more likely to develop dementia after a decade of auditory deprivation, and those with severe hearing loss are five times more likely. While it cannot be concluded based on this relationship that hearing loss causes dementia, the strength of the relationship is sufficient to warrant a hypothesis that keeping the auditory pathways stimulated and functioning properly could potentially have a preservation effect.  At least 36 million people in the United States suffer from hearing loss, yet only about 8 million of these individuals use amplification devices, in spite of an enormous amount of evidence supporting the benefits of doing so (NCOA, 1999). 

Typical barriers to following through on a recommendation to pursue hearing aids include cost and the unfortunate stigma associated with hearing aids. Another significant barrier is the lack of a standard referral process. The Audiology community has efforts underway to educate the public about seeking help for hearing loss earlier in life, as well as educating primary care physicians abut the importance of annual hearing screenings starting as early as age 45 years.  It is not unusual for hearing loss to begin developing around this age and progress unnoticed for a number of years, since it is such a gradual change over a long period of time.  Affected individuals often adjust to these changes over time without realizing it.  Once the hearing loss becomes more obvious, brain reorganization has already been initiated and can interfere with the ability to adapt to the hearing aids.  This phenomenon is the culprit for many dissatisfied hearing aid users, creating an unfortunate Catch 22 that prevents motivation to use amplification. This, in turn, leads to even longer periods of auditory deprivation for the person with hearing loss, further compounded by symptoms of depression and isolation.   

If you or a loved one are over age 45 and have not had a hearing screening within the last year, please schedule an appointment at The Hearing Center at Bridgewater Falls!  Annual hearing screenings allow us to compare and monitor changes over time. Let us keep you informed of your hearing status and possibly help reduce further negative impact. Timely intervention for a developing hearing loss could mean a world of difference in many aspects of life!  We look forward to hearing from you!

References:

Francis HW, Chee N, Yeagle J, et al. (2002). Impact of cochlear implants on the functional health status of older adults. Laryngoscope, 112(8 Pt 1):1482–8.

Gopinath B, Wang JJ, Schneider J, et al. (2009). Depressive symptoms in older adults with hearing impairments: the Blue Mountains Study. J Am Geriatr Society, 57(7):1306–8.

Hallam R, Ashton P, Sherbourne K, et al. (2006). Acquired profound hearing loss: mental health and other characteristics of a large sample. Int J Audiology, 45(12):715–23.

Lin FR, Metter EJ, O’Brien RJ, et al. (2012) Hearing loss and incident dementia. Arch Neurology, 68:214–20.

National Council on Aging, (1999). Untreated Hearing Loss Linked to Depression, Anxiety, Social Isolation in Seniors. www.ncoa.org.  

Peelle JE, Troiani V, Grossman M, et al. (2011). Hearing loss in older adults affects neural systems supporting speech comprehension. J Neuroscience, 31(35):12638–43.

Poissant SF, Beaudoin F, Huang J, et al. (2008). Impact of cochlear implantation on speech understanding, depression, and loneliness in the elderly. J Otolaryngol Head Neck Surgery, 37(4):488–94.