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Dementia

NEW EVIDENCE ON THE DANGERS OF UNTREATED HEARING LOSS

Hearing Loss May Signal Increased Dementia Risk.

In recent years, researchers around the world have discovered that there are scientific reasons to address hearing loss earlier. Seniors with hearing loss are significantly more likely to develop dementia over time than those who retain their hearing. Although the exact reason for the link between hearing loss and dementia is unknown, the investigators suggest that a common pathology may or both the strain of trying to decode sounds over the years may overwhelm the brain of people with hearing loss leaving them more vulnerable to dementia. Hearing is a special gift and our ability to hear sounds is essential to our enjoyment and well being. Hearing loss could lead to dementia by making individuals more socially isolated. Low levels of social engagement have been shown to increase the risk for Alzheimer’s disease.

UNDERSTANDING SPEECH – “USE IT OR LOSE IT”

As hearing is lost with increasing age, a person’s ability to understand speech in an unaided ear deteriorates faster over time than his ability to understand speech in an aided ear. For most people this is reversible if a hearing aid is fitted to the unaided ear. However, if the period without a hearing aid extends over some years, then full recovery is unlikely. THAT IS, IF WE DON’T USE IT, WE MAY LOSE IT.

NEUTRAL BRAIN PLASTICITY – We listen with our ears but hear with our brains

Research has shown that we listen with our ears but hear with our brains. It is not possible to separate audition (hearing) and cognition (brain). When neurons (brain cells) in that area of the brain responsible for understanding speech are denied stimulation due to hearing loss, the brain will reprogram those neurons to do something else and that comes at the expense of cognition. This may in part explain why straining to hear conversations over background noise can be mentally exhausting for anyone. The fitting of hearing aids sooner rather than later can significantly delay this unwanted process i.e., “USE IT OR LOSE IT “, or the brain will start doing something else.

DEMENTIA

In a large study over some 20 years*, researchers found that patients with hearing loss at the beginning of the study were significantly more likely to develop dementia by the end of the study. The greater the hearing loss, the more likely they were to develop dementia. Even after all other risk factors for dementia were accounted for, hearing loss and dementia were still strongly connected.

Another good reason to treat hearing loss early rather than waiting until it is a significant social problem.

Whatever the cause, the scientists report, their finding may offer a starting point for interventions — even as simple as hearing aids — that could delay or prevent dementia by improving patients’ hearing.

Clinical Interests:

  • Hearing rehabilitation in aging populations.
  • Cochlear implantation.
  • Bone anchored and implantable hearing devices.
  • Chronic ear surgery.

Dr Lin’s research focuses on how hearing loss impacts the health and functioning of older adults and the role of different treatment modalities (hearing aids, cochlear implantation) in mitigating these effects. In particular, he is interested in examining the potential causal associations between hearing loss and dementia, cognition, functional decline, social isolation, and health economic costs. Much of his research is conducted in collaboration with aging researchers and established centres for clinical and aging research such as the Longitudinal Studies Section of the National Institute on Aging, the Johns Hopkins Center for Aging and Health, and the Johns Hopkins Dana Center for Preventive Ophthalmology.

Hearing loss in older adults is independently associated with an increased risk of developing dementia over time, new findings from the Baltimore Longitudinal Study on Aging suggest.

“Whether hearing loss is a marker for early-stage dementia or is actually a modifiable risk factor for dementia deserves further study,” concludes the study team in the February 2011 issue of Archives of Neurology.

“We’ll need to do more research to figure out what the exact mechanism may be and whether interventions such as hearing aids or cochlear implants could have an effect on delaying cognitive decline,” first study author Frank R. Lin, MD, PhD, of the Center on Aging and Health, Johns Hopkins Medical Institutions, in Baltimore, Maryland, told Medscape Medical News.

“Including hearing in a neurologic assessment is long overdue,” said George A. Gates, MD, of the University of Washington in Seattle, who was not involved in the study. Dr. Gates’ own research has also shown a link between hearing difficulties and dementia.

Credit:

Frank R. Lin , M.D. Ph.D.

Assistant Professor, Division of Otology, Neurotology and Skull Base Surgery Assistant Professor, Department of Epidemiology, Bloomberg School of Public Health

Core Faculty Member, Johns Hopkins Centre on Ageing and Health.

Footnotes:

http://www.hopkinsmedicine.org/otolaryngology/our_team/faculty/ lin_frank.html

http://www.hopkinsmedicine.org/otolaryngology/ http://www.grc.nia.nih.gov/branches/blsa/blsanew.htm

Arch Neurol. 2011;68:214-220. Abstract

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