We have all by now read the lurid headlines in relation to the ongoing research into untreated hearing loss and its apparent link to neurocognitive disorders like Dementia. Headlines like the one above are likely to strike fear into people. But hey, that is what sells Newspapers, let's take a closer look at the evidence.
In the recent past, there has been a lot of news articles talking about the effects of untreated hearing loss. Many of them focus on the effects of untreated hearing loss on the brain. From the studies that they quote, there appears to be a link between untreated hearing loss and cognitive diseases like Alzheimers and dementia.
Update: In a report presented July 20 at the Alzheimer’s Association International Conference 2017 (AAIC 2017) in London, The Lancet International Commission on Dementia Prevention, Intervention, and Care said that more than one-third of global dementia cases may, in fact, be preventable. They believe that there is the possibility to prevent dementia through addressing lifestyle factors that impact an individual’s risk. The AAIC announced. These potentially modifiable risk factors—which included hearing loss—have been identified at multiple phases across the lifespan, not just in old age.
"Our results suggest that around 35 percent of dementia is attributable to a combination of the following nine risk factors: education to a maximum of age 11-12 years, mid-life hypertension, mid-life obesity, hearing loss, late-life depression, diabetes, physical inactivity, smoking, and social isolation," the study said. You can see more about this in the new article Untreated Hearing Loss & The Dementia Connection
Again, this should be treated as further weight of evidence in relation to untreated hearing loss and cognitive decline. The study is not definitive, but for the AAIC to make a statement such as this, it means that they feel there is a great deal of veracity in the link.
A Careful Reading of The Facts
It is important that we carefully look at the facts that we know, those facts need to be based on scientific study. The facts are not so clear-cut as the headlines would have you believe, yes it appears that there is a link, but it is by no means a causative link. Let me explain, the outcome of a study can show no link, a causative or causal link or a correlative link.
Causative links are proven links, for instance, smoking is a causative link for cancer. We know after much study that smoking has a direct link to the causation of cancer. Correlative links are different when something is correlative, it means that we know that when one thing happens it is often the case that something else is happening.
The data has not reached the stage where we can say there is a definite causative link. In fact, the data may never exist, it could be proved that there was ever only a correlative relationship. With this in mind I want to review a couple of studies in relation to cognitive decline, hearing loss and hearing aid use.
The Link Between Hearing Loss & Cognitive Disorders
What we do know is that studies show a very strong causative link between untreated hearing loss and more rapid cognitive decline. These studies only address the link between the hearing loss and the rate of cognitive decline. They show that there is a link between untreated hearing loss and more rapid cognitive decline in the people who suffer it. They do not show that that cognitive decline is directly linked to or may lead to Dementia or other cognitive disorders.
A study undertaken by Deal et al(1) show that the rate of 20-year memory decline for people with untreated hearing loss in a group, was twice the average rate of decline reported in national studies of cognitive change in older adults (Salthouse, 2010; Hayden et al., 2011). In comparison, the hearing aid users in this study with moderate/severe hearing loss showed a rate of cognitive decline that was only slightly higher than the rate for subjects with normal hearing. This seems to prove that treating hearing loss when needed reduces cognitive decline.
This study was undertaken over a long period with 253 subjects. It shows that there is more than a passing relationship between untreated hearing loss and more rapid cognitive decline. It is thought that the cognitive decline could be related to hearing loss may be correlated with temporal lobe and whole brain atrophy(brain shrinkage)(2) (Lin & Albert, 2014; Peelle, et al., 2011; Lin et al., 2014 ). It is thought that increased social isolation, increased perceptual effort and changes in brain volume are related to the cognitive decline. However, and this is what matters, whether the two conditions are related to a shared underlying cause is not yet known.
More Evidence That Hearing Aids Reduce Cognitive Decline
Another long-term study shows that wearing hearing aids reduces the more rapid cognitive decline associated with hearing loss. it underlines the importance of having hearing loss treated at the earliest possible opportunity. It also shows that hearing loss is a more important health issue then is generally appreciated.
“Self-Reported Hearing Loss: Hearing Aids and Cognitive Decline in Elderly Adults: A 25-year Study,” (3) was published in the October edition of the Journal of the American Geriatrics Society. The study compared cognitive decline among older adults who were using hearing aids and those who were not. The study found that there was no difference in the rate of cognitive decline between a control group of people with no reported hearing loss and people with hearing loss who used hearing aids. However, untreated hearing loss was significantly associated with lower baseline scores on the Mini-Mental State Examination, a well-established test of cognitive function.
Professor Hélène Amieva, a leading researcher in the Neuropsychology and Epidemiology of Aging at the University of Bordeaux, France, headed up the study. The study followed a massive 3,670 adults, age 65 and older over a 25-year period as part of the Personnes Agèes QUID cohort (PAQUID), a cohort specifically designed to study brain aging.
Evidence That Hearing Aids May Improve Cognitive Function
A recent study by Jamie Desjardins, PhD, an assistant professor in the speech-language pathology program at The University of Texas at El Paso, has shown that hearing aids actually improve the function of the brain in people with hearing loss. We know that untreated hearing loss can lead to emotional and social difficulties, reduced job performance, and a diminished quality of life. As people age, cognitive skills like working memory, the ability to pay attention to a speaker in a noisy environment, or the ability to process information rapidly, begin to decline.
The study was designed to explore the effects of hearing loss on brain function. The study was undertaken on a group of individuals in their 50s and 60s with bilateral (both ears) sensorineural hearing loss who had never used hearing aids. The study participants took cognitive tests to measure their working memory, selective attention, and processing speed abilities before and after using hearing aids.
Two Weeks Of Hearing Aid Use Showed Improvement
Just two weeks of hearing aid use showed improvements in cognitive abilities, tests revealed an increase in percent scores for recalling words in working memory and selective attention tests. They also showed an increase in cognitive processing speed, in essence the time for participants to select the correct response was faster. By the end of the study, participants had shown significant improvement in their cognitive function..
Will Hearing Aids Slow or Prevent Dementia?
That is a question that can not be answered yet, simply because we don't have enough evidence that untreated hearing loss directly contributes to Dementia in one way or the other. We know that they certainly seem to exist together in many cases. This is an emerging area of study, the results reported here offer strong support that the risk of rapid cognitive decline caused by hearing loss can be reduced, by treating hearing loss with hearing aids.
We do know that hearing aids are an effective way to improve communication and decrease social isolation. We now know that hearing aids will slow the more rapid cognitive decline seen in people with untreated hearing loss. What effect that will have on the onset of Dementia or other cognitive disorders is questionable.
It is clear that the two conditions are related and because hearing loss is easily treatable it may be one of the few ways in which someone can take steps to manage their risk of cognitive decline.
In essence, judgement is still reserved here except for one thing we do know, it is always a good idea to treat hearing loss. We hope we have given enough clear information here, if you have any questions, don't hesitate to contact us.
1. Deal, J., Sharrett, A., Albert, M., Coresh, J., Mosley, T., Knopman, D., Wruck, L. & Lin, F. (2015). Hearing impairment and cognitive decline: A pilot study conducted within the Atherosclerosis Risk in Communities Neurocognitive Study. American Journal of Epidemiology 181 (9), 680-690.
2.Lin, F. & Albert, M. (2014). Hearing loss and dementia – who is listening? Aging and Mental Health 18(6), 671-673.
3.Amieva H, Ouvrard C, Giulioli C, Meillon C, Rullier L, Dartigues JF. Self-Reported Hearing Loss: Hearing Aids and Cognitive Decline in Elderly Adults: A 25-year Study,J Am Geriatr Soc. 2015 Oct;63(10):2099-104. doi: 10.1111/jgs.13649.
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