February 8, 2018. Recently, the Globe and Mail ran an article on a possible link between hearing loss and dementia (See https://www.theglobeandmail.com/life/health-and-fitness/health-advisor/what-we-know-about-the-link-between-hearing-loss-and-dementia/article37761654/). The article was based on a 2011 paper “Hearing Loss and Incident Dementia” detailing the outcome of a 15 year study of 639 adults at John Hopkins University. When the study began, 25% of the participants had hearing loss. When the study ended, those with the severest hearing loss seemed to have the greater incidence of dementia.
Ever since the initial report came out, a link between hearing loss and dementia has been bandied about. But how valid is this potential link? Many of us have had hearing loss for decades and do not have any symptoms of dementia. Many of us know people who do not have hearing loss, but do have dementia. Maybe there is more to the story?
A few years ago, my husband and I attended a presentation on dementia from a Boston-based researcher specializing in the subject. Several people in the audience either had Alzheimer’s or other forms of dementia, or were family members of those with dementia, while the rest were like us, hoping to learn how to avoid dementia. People asked if doing crosswords and Sudoku would help. Not really, we learned. What about speaking several languages? Not really. The two most common tips to avoid dementia that had been discussed for years were now shot down.
So what would help? The researcher discussed the link between genetics and dementia – if you have a family history of dementia, you may be more susceptible. He then discussed how environment and chemicals can play a role. Diet is a factor and he suggested that sugar is not our best friend. Exercise is also important as a sedentary lifestyle is a risk factor. High blood pressure (hypertension) and diabetes are additional risk factors.
He then said that although these factors mentioned play a part, there are two very important preventative measures that can overcome many of the risk factors mentioned above. These two preventative measures are:
- Have an active social life.
- Always learn something new
That was it. Two key preventative measures: Avoid social isolation and stretch your mind by keeping it actively learning something new. Both of these force the brain to rewire itself and develop new pathways, which in turns keeps us mentally alert.
So what did the John Hopkins study say? (Read the report: Hearing Loss and Incident Dementia nihms-336097) In the paper’s introduction it noted that ongoing studies have focused on the risk factors for prevention, based “on the assumption that dementia is easier to prevent than to reverse. Candidate factors include low involvement in leisure activities and social interactions, sedentary state, diabetes, and hypertension. Some researchers have also suggested that hearing loss, by reducing stimulatory input and hampering social interaction, may be associated with dementia.” In other words, are social isolation and not keeping the brain active factors?
The study then discussed possible incorrect diagnoses and explained why the researchers in the study had eliminated them. The incorrect diagnoses included:
- Over-diagnosis of dementia in individuals affected by hearing loss
- Over-diagnosis of hearing loss in individuals with cognitive impairment at baseline (ie, when the study began)
The study looked at two other factors that could have affected their results, and explained that they did not believe these were factors in the study results. These factors were:
- Both hearing loss and progressive cognitive impairment are caused by a common neuropathologic process. In other words, they looked at whether hearing loss and dementia were caused by the same condition.
- The likelihood that another neurobiological process such as vascular disease or factors related to family history could cause both hearing loss and dementia. In other words, could another condition cause both hearing loss and dementia? Their study could not exclude this factor, but they noted that “risk factors for vascular disease such as diabetes, smoking, and hypertension were adjusted for in our models.”
The researchers then noted that “hearing loss may be causally related to dementia, possibly through exhaustion of cognitive reserve, social isolation, environmental deafferentation, or a combination of these pathways.” Quite a mouthful, isn’t it? What do they mean?
In explaining cognitive reserve, they noted that when it’s hard to hear due to hearing loss, “greater cognitive resources” (ie brain power) “are dedicated to auditory perceptual processing“ (ie figuring out what someone said) “to the detriment of other cognitive processes such as working memory.” So, basically they are saying that your brain’s memory capacity is similar to a computer’s temporary memory. If you’ve ever had to shut down your computer and restart it to get it working properly again, then you can understand what is happening with your own brain power. It gets overloaded and tired and needs a rest to get going again. You may forget things or get confused because your brain’s cognitive resources are overworked. Normally, this is temporary, and once you have given your mind a chance to rest with quiet time, you will be fine.
Environmental deafferentation (the elimination of sensory nerve fibres) is a technical way of saying that something like this can happen: When someone speaks to you, they assume you can hear everything you are saying. But those of us with hearing loss know that we sometimes find it hard to hear exactly what is being said, and we guess what the missing word or phrase is. If we guess wrong, we give the wrong response.
The study goes on to suggest that “this reallocation of neural resources to auditory processing could deplete the cognitive reserve available to other cognitive processes and possibly lead to the earlier clinical expression of dementia neuropathology.” So make sure you rest!
Next the researchers explain that “communication impairments caused by hearing loss can also lead to social isolation in older adults and studies have demonstrated associations between poor social networks and dementia.” The message: social isolation is bad. “Individuals who remain engaged in leisure activities have a lower risk of dementia.”
The researchers briefly discuss studies in mice in which they found that “environmental enrichment (possibly analogous in humans to having access to auditory and environmental stimuli) can reduce β-amyloid levels.” β-amyloid is the protein that is believed to cause dementia.
The study then concludes with the statement that “self-reported hearing aid use was not associated with a significant reduction in dementia risk.” So, while a hearing aid may help reduce your brain’s cognitive load in hearing what is being said, it will not reduce the risk of dementia. For that you need to turn to the same key factors as with everyone else – keep active socially and keep stimulating your mind.
The researchers in the study note that “ongoing research is needed as to whether hearing advices and rehabilitative strategies could have an effect on cognitive decline and dementia.” Hmmm… why wait? We already have a blueprint for some preventative strategies. So go out for dinner and enjoy socializing with your friends, eat well, make sure you get some physical exercise, and stimulate your mind by learning something new.
We’d like to have your tips and strategies for keeping your mind active and in good working order, even though you have a hearing loss. As for me, I keep very active socially and every year I tackle a new project to keep those brain cells stretching. Over the years I’ve learned Latin to be able to read family history records, taken art lessons, last year it was blog writing. This year? I’m still pondering. Maybe I need to have a restful Caribbean beach vacation to get those “cognitive resources” in good working order again!
Next Chapter meeting: Tuesday, April 10, 2018 at North Tryon Presbyterian Church
Do you have a story or tip about hearing loss issues that are important to you? Comments can be made on this blog, or you can email us at email@example.com.
© Daria Valkenburg