According to Herbert, Weuve, Scherr and Evans (2013), 4.7 million Americans over the age of 65 were diagnosed with dementia. Audiology today (2014) reports 40% of those over 65 years old will present with hearing loss and 66% over 75 will have hearing loss. In 2011, a link between hearing loss and cognitive decline was discovered. How has hearing loss been linked to dementia?
Researchers at John Hopkins School of Medicine looked at 639 adults from 36-90 years of age for 12 years and monitored cognitive health and hearing health. While none of the subjects had dementia at the start of the study, 184 of the 639 subjects had some degree of hearing loss. Researcher, Otologist and Epidemiologist Dr. Frank Lin discovered a link between those who had hearing loss at the beginning of the study and those who developed dementia at the end of the study. Linn and his associates also found the greater the hearing loss, the more chance of developing dementia and with every 10 decibels of hearing loss, the likelihood of dementia increased by 20%.
In 2013, another study revealed similar results. Lin looked at nearly 2000 adults and found those with hearing loss experienced more loss of memory, concentration or thinking capabilities 40% faster than those with normal hearing. He also found accelerated rates of brain atrophy in those with hearing loss compared with those with normal hearing. Dr. Arthur Wingfield, professor of neuroscience at Brandeis University, studied brain volume using MRI’s and found that those with poorer hearing show that the frontal part of the brain works harder. Wingfield concluded that this effort to try to listen and comprehend may take a toll on cognitive resources.
This link of hearing loss and dementia is also backed by researcher Dr. Richard Gurgel. Gurgel (2014) studied 4400 adults over the age of 65 and found that those with hearing loss at the beginning of the study developed dementia at a higher rate and earlier than those with normal hearing.
Why is there a link?
Three Theories exist according to Lin:
- Cognitive Overload: The brain works harder to cope when sounds are degraded.
- Brain Atrophy: Hearing loss may contribute to accelerated rates of atrophy in parts of the brain that process sound, which may also involve vascular aspects.
- Social Isolation: Those who have difficulty hearing may withdraw from social situations. Numerous studies have found that a loss of engagement and loneliness are risk factors for cognitive decline.
Will treating hearing loss reduce the risk of dementia?
Frank Lin and his team are currently looking for answers and conducting a 5-year study with 800 older adults. Since we already know hearing impairment is independently associated with a 30-40% rate of accelerated cognitive decline, Lin will look at whether treating hearing loss will reduce this risk factor of dementia. In this study, some of the subjects will receive state-of-the-art hearing technology and others will only receive “wellness advice.” Cognitive decline of the subjects will be measured at the end of the study. If Lin’s study finds the risk factors for cognitive decline are modifiable, then recommending hearing loss treatment will become a priority. Results of this study could provide promising results.
I will keep you posted on new discoveries.
References
Herbert, L., Weuve, J. Scherr, P., Evans, D. (2013). Alzheimer disease in the United States (2010-2050) estimated using the 2010 census. Neurology 80, 1778-1783.
Jorgensen, L. (2014). Evaluation of hearing status at the time of dementia diagnosis. Audiology Today, 39-44.
Lin, FR, Albert, M. (2014). Hearing loss and dementia, who’s listening? Aging Mental Health, 18, 671-673.
Lin FR, Metter EJ, O’Brien RJ, Resnick SM, Zonderman AB, Ferrucci L. (2011). Hearing loss and incident dementia. Arch Neurology. 68,(2), 214–220. doi: 68/2/214 [pii] 10.1001/archneurol.2010.362
Lin FR, Yaffe K, Xia J, Xue QL, Harris TB, Purchase-Helzner EL, Simonsick E. (2013). Hearing loss and cognitive decline among older adults. JAMA Internal Medicine
Rokins, T. (2013). The links between hearing loss and dementia. The Huffington Post.