New research shows link between hearing loss and dementia

Posted on: 14 December 2017

Researchers from Trinity have found, in a new study, that hearing loss in older adults is associated with cognitive decline and dementia.

The researchers from Trinity’s Institute of Neuroscience and Global Brain Health Institute made the findings following a comprehensive review of 36 previous studies from 12 countries involving 20,264 participants — the biggest study to date of hearing loss, cognitive decline and dementia. The research was recently published in JAMA Otolaryngology – Head & Neck Surgery.

A significant number of previous studies have looked at hearing loss and its possible association with cognitive decline and dementia in large cohorts of adults. However, while some of these studies have reported that there is an association between cognitive decline and hearing loss, other studies have reported that there is little or no association.

This review was conducted to investigate this association and to clarify it. Only observational studies that used standard cognitive tests and pure-tone audiometry (the clinical standard for assessment of peripheral hearing loss) were included. These inclusion criteria, in addition to combining data from multiple studies, allowed for a more accurate assessment of the relationship between hearing loss and cognition.

The results showed that people with age-related hearing loss had an increased risk for cognitive decline including executive function, processing speed and episodic memory. They also had a higher risk for cognitive impairment and dementia.

As this wasn’t a clinical trial, the researchers don’t yet know if there is a causal relationship or what the reasons for the connection are, and stress that further research is needed to determine this. However, the association is comparable in size to other potentially modifiable risk factors for dementia such as depression, smoking and hypertension.

There are a number of hypotheses for the connection such as a common causal pathway and a mechanistic pathway, such as reduced cognitive stimulation. Hearing loss may cause diversion of mental resources to perceive speech, leaving fewer resources available for other processes such as memory. Additionally, research suggests that factors such as depression or loneliness may be associated with a higher risk of dementia. These factors may explain the association between hearing loss and cognitive decline.

Speaking about the implications of this study for future research, lead author, PhD student and Atlantic Fellow at the Global Brain Health Institute at Trinity, David Loughrey, said: “We need intervention trials that look at the benefits of hearing loss treatment over a long follow-up period to see if it deceases the risk of someone getting dementia.”

It’s too early for GPs to tell their patients that if their hearing loss is addressed this will lower their risk of getting dementia. A hearing problem can certainly contribute to difficulty with uptake of information and for this reason should be addressed.  

Dementia affects about 46.8 million people worldwide and this is estimated to grow to 131.5 million by 2050. Approximately one third of adults older than 65 experience a disabling hearing loss and, in many cases, it is untreated.

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