How hearing loss in old age affects the brain
April 23, 2020
Science Daily/Ruhr-University Bochum
If your hearing deteriorates in old age, the risk of dementia and cognitive decline increases. So far, it hasn't been clear why. A team of neuroscientists has examined what happens in the brain when hearing gradually deteriorates: key areas of the brain are reorganized, and this affects memory.
Daniela Beckmann, Mirko Feldmann, Olena Shchyglo and Professor Denise Manahan-Vaughan from the Department of Neurophysiology of the Medical Faculty worked together for the study.
When sensory perception fades
The researchers studied the brain of mice that exhibit hereditary hearing loss, similar to age related hearing loss in humans. The scientists analysed the density of neurotransmitter receptors in the brain that are crucial for memory formation. They also researched the extent to which information storage in the brain's most important memory organ, the hippocampus, was affected.
Adaptability of the brain suffers
Memory is enabled by a process called synaptic plasticity. In the hippocampus, synaptic plasticity was chronically impaired by progressive hearing loss. The distribution and density of neurotransmitter receptors in sensory and memory regions of the brain also changed constantly. The stronger the hearing impairment, the poorer were both synaptic plasticity and memory ability.
"Our results provide new insights into the putative cause of the relationship between cognitive decline and age-related hearing loss in humans," said Denise Manahan-Vaughan. "We believe that the constant changes in neurotransmitter receptor expression caused by progressive hearing loss create shifting sands at the level of sensory information processing that prevent the hippocampus from working effectively," she adds.
https://www.sciencedaily.com/releases/2020/04/200423130446.htm
Sensory impairment and health expectancy in older adults
August 15, 2019
Science Daily/Duke-NUS Medical School
Older adults aged 60 years and above with vision and hearing impairments may enjoy fewer years of life as well as healthy life compared to those with no impairments. Detecting and managing these conditions early could prolong the duration of life lived in good health by older adults, a new study suggests.
Out of the five physical senses, impairment in vision and hearing, especially simultaneously, may have the greatest impact on the health of older adults. These impairments are associated with poor health outcomes, such as limitations in physical function and activities of daily living (ADLs), social isolation, cognitive decline, depression, poor self-rated health (SRH), communication difficulties, and even mortality. Studying the effect of vision and hearing impairment on life expectancy and health expectancy -- the duration of remaining life expected to be spent with (or without) health problems -- in older adults is relevant because these impairments affect both the quality and the quantity of life. This would allow care providers, policy makers and older adults and their families to thoroughly understand the impact of these common, yet often treatable, impairments.
"We investigated how vision and hearing impairments impact life expectancy and health expectancy among older adults. We were specifically interested in understanding how these impairments affect health expectancy when health is defined by a) physical function and b) the ability to perform activities of daily living (ADLs) -- two important health indicators among older adults," said Dr Rahul Malhotra, Head of Research, Centre for Ageing Research and Education, Duke-NUS, and senior author of the study. Dr Malhotra is also an Assistant Professor with the Duke-NUS Health Services and Systems Research Programme (HSSR).
The researchers asked participants to rate their own vision and hearing abilities. To assess physical function, they asked participants to report whether they had trouble with tasks involving their arms and legs, such as walking 200-300 metres, climbing ten steps without resting, or raising their hands above their heads. They also asked participants to report whether they had trouble completing basic ADLs, including bathing, dressing or eating, or instrumental ADLs, such as doing housework, managing their medications or taking public transport.
They found that, at ages 60, 70 and 80, people with either or both vision and hearing impairments could expect more years of remaining life with limited physical function as well as with limitations in ADLs, compared to those without impairments.
People with both hearing and vision impairments had the greatest reduction in health expectancy, as well as an overall lower life expectancy. For example, at age 60, those with both impairments could expect not only a life expectancy that was about four years shorter than unencumbered participants, but also about three more years of life with limitation in physical function. Older adults with both impairments could expect to spend 62% of their remaining life with limitation to physical function, while the estimated figure for those with neither impairment was 38%. In addition, older adults with both impairments could expect to spend nearly one-third (31%) of their remaining life with limitation in ADLs, while those with neither impairment could expect only 16%.
"What's unique about our study is that we allowed vision and hearing impairment status to vary over time in the analysis. This is reflective of real-life cases, where some people would progress in their impairment over time, while others would remain stable or improve upon treatment of the underlying cause. We also accounted for the respondents' existing chronic diseases," said Dr Chan Wei-Ming Angelique, Executive Director, Centre for Ageing Research and Education, Duke-NUS, and co-author of the study. Dr Chan is also an Associate Professor with the Duke-NUS' HSSR.
"Vision and hearing impairments are often perceived as an unfortunate but inconsequential part of ageing, and in many cases, remain undetected or untreated. This important study by our researchers shows that early detection and timely management of vision and hearing impairments by older adults, their families and health systems are key to increasing the quality of life for older adults," said Professor Patrick Casey, Senior Vice Dean for Research at Duke-NUS.
The team is planning to compare this study's findings, which was based on self-reported vision and hearing impairment, with objectively measured impairment status by other groups in Singapore and around the world.
https://www.sciencedaily.com/releases/2019/08/190815093101.htm
With age comes hearing loss and a greater risk of cognitive decline
But study suggests higher education might counter effects of milder hearing impairment
February 12, 2019
Science Daily/University of California - San Diego
In a new study, researchers report that hearing impairment is associated with accelerated cognitive decline with age, though the impact of mild hearing loss may be lessened by higher education
Hearing impairment is a common consequence of advancing age. Almost three-quarters of U.S. adults age 70 and older suffer from some degree of hearing loss. One unanswered question has been to what degree hearing impairment intersects with and influences age-related cognitive decline.
In a new study, researchers at University of California San Diego School of Medicine report that hearing impairment is associated with accelerated cognitive decline with age, though the impact of mild hearing loss may be lessened by higher education.
The findings are published in the February 12, 2019 issue of the Journal of Gerontology: Series A Medical Sciences.
A team of scientists, led by senior author Linda K. McEvoy, PhD, professor in the departments of Radiology and Family Medicine and Public Health, tracked 1,164 participants (mean age 73.5 years, 64 percent women) in the longitudinal Rancho Bernardo Study of Healthy Aging for up to 24 years. All had undergone assessments for hearing acuity and cognitive function between the years 1992 to 1996 and had up to five subsequent cognitive assessments at approximately four-year intervals. None used a hearing aid.
The researchers found that almost half of the participants had mild hearing impairment, with 16.8 percent suffering moderate-to-severe hearing loss. Those with more serious hearing impairment showed worse performance at the initial visit on a pair of commonly used cognitive assessment tests: the Mini-Mental State Exam (MMSE) and the Trail-Making Test, Part B. Hearing impairment was associated with greater decline in performance on these tests over time, both for those with mild hearing impairment and those with more severe hearing impairment.
However, the association of mild hearing impairment with rate of cognitive decline was modified by education. Mild hearing impairment was associated with steeper decline among study participants without a college education, but not among those with higher education. Moderate-to-severe hearing impairment was associated with steeper MMSE decline regardless of education level.
"We surmise that higher education may provide sufficient cognitive reserve to counter the effects of mild hearing loss, but not enough to overcome effects of more severe hearing impairment," said McEvoy.
Degree of social engagement did not affect the association of hearing impairment with cognitive decline. "This was a somewhat unexpected finding" said first author Ali Alattar. "Others have postulated that cognitive deficits related to hearing impairment may arise from social isolation, but in our study, participants who had hearing impairment were as socially engaged as those without hearing loss."
The findings, said the authors, emphasize the need for physicians to be aware that older patients with hearing impairments are at greater risk for cognitive decline. They also emphasized the importance of preventing hearing loss at all ages, since hearing impairment is rarely reversible. One important way to protect hearing, they said, is to minimize loud noise exposure since this is the largest modifiable risk factor for hearing impairment.
https://www.sciencedaily.com/releases/2019/02/190212134802.htm