by Daniel Fink, MD, Chair, The Quiet Coalition
Bryan Pollard, founder of Hyperacusis Research, Ltd., is an electrical engineer. Almost every time I have discussed something with him, he asks me an important question: “What’s the cause? What’s the effect?”
It is very easy to make a mistake thinking that an association is causal when it is not.
One of the best ways to avoid making this mistake is to study a phenomenon over time. If a factor in some research subjects is associated with changes over time, and absence of that factor is not associated with the change being examined, causality is more likely.
A good example of this question is the association of hearing loss with the development of dementia. Maybe hearing loss causes dementia because there is decreased nerve stimulation of certain parts of the brain related to auditory and speech processing, but maybe the brain changes are independent of hearing loss or perhaps even the cause of the hearing loss.
This recent report in JAMA Otolaryngology-Head and Neck Surgery, with an accompanying editorial, uses the study of brain changes over time to try to answer this question. The research was done on the well-studied population of the Baltimore Longitudinal Study of Aging. Hearing tests and studies of brain tissue using specialized research techniques were done. Imaging was done by MRI at the National Institute of Aging.
Results showed that poorer hearing at baseline was associated with specific changes in portions of the brain processing auditory input, but not in other areas of the brain. The editorial notes the limitations of the study and its preliminary nature, but the report is another piece of the puzzle linking hearing loss to dementia.
For at least five years, I have been saying, “If it sounds too loud, it IS too loud.” But based on the accumulating evidence of the dangers of noise for hearing loss, and then the impact of hearing loss on social function, economic success, and the development of dementia, I’ve decided to change my advice.
Now I would say, “If it sounds loud, it IS too loud.”