Hormone linked to good hearing as we age

Hormone linked to good hearing as we age

Researchers have linked a hormone known to adjust levels of key brain chemicals to the quality of our hearing as we age. The more of the hormone that older people have in their bloodstream, the better their hearing is, and the less of the hormone, the worse their hearing is.

The hormone, aldosterone, is known to regulate kidney function and also plays a role in controlling levels of two crucial signaling chemicals in the nervous system, potassium and sodium. For nerves to send signals crisply and work properly, potassium and sodium must be in precise proportion, without any disruption in the molecular channels or gates through which they move. Levels of potassium are particularly crucial in the sensitive inner ear, where fluid rich in potassium plays a central role in converting sounds into signals that the nervous system recognizes.

The team of scientists in Rochester, N.Y., put 47 healthy men and women between the ages of 58 and 84 through a battery of sophisticated hearing tests. Scientists also measured their blood levels of aldosterone, which is known to drop as people age. They found that people with severe hearing loss had on average about half as much aldosterone in their bloodstream as their counterparts with normal hearing. The researchers noted, however, that the levels of aldosterone found in all the participants is considered normal, and that no patients or physicians should consider altering aldosterone levels without more research.

The findings come from researchers at the International Center for Hearing and Speech Research (ICHSR), a group funded by the National Institute on Aging that is recognized as a leader in research on age-related hearing loss. The center includes scientists from the National Technical Institute for the Deaf at Rochester Institute of Technology and neuroscientists from the University of Rochester.

"The inner ear is especially sensitive to any disruption in potassium levels," said Robert D. Frisina, Ph.D., professor of Otolaryngology at the University of Rochester Medical Center and an adjunct professor at Rochester Institute of Technology. "We know that potassium levels in the inner ear seem to decrease as we age and that these falling levels play a role in age-related hearing loss, and we also know that blood levels of aldosterone generally decrease with age.

"We found a direct link between blood levels of aldosterone and the ability of people to hear normally as they age. Depressed hormone levels may hurt hearing both in the inner ear and the part of the brain used for hearing. More research is needed, however, to understand the precise role that aldosterone plays – for instance, whether it's a cause of failed hearing, or whether it's symptomatic. Before we understand the issue more fully, people should not worry about their aldosterone levels or look to boost the amount in their bloodstream."

The team led by Frisina published its results in the November issue of the journal Hearing Research. This week at the annual international meeting of the Association for Research in Otolaryngology in Baltimore, the team presented its latest results showing just how important potassium regulation is to age-related hearing loss.

In Baltimore, Otolaryngology medical resident Jared Spencer, M.D., presented results from "knockout" mice whose genes controlling the potassium channels in the inner ear don't function properly, and confirmed that malfunctioning potassium channels are central to age-related hearing loss, or presbycusis. The channels are highly concentrated in a part of the brain that plays an important role providing feedback from the brain to the ears. Frisina's team previously discovered that the feedback system is one of the first things to go wrong in age-related hearing loss, often declining in people who are in their 40s and 50s, usually before they even realize their hearing is declining.

"We are now working out some of the underlying biology about how the decline occurs," said Frisina. "We have evidence that these potassium channels may play an important role in the failure of the feedback system, which is a big part of age-related hearing loss."

Nearly everyone wrestles with failing hearing at some point. While some people suffer from hearing damage as a result of exposure to loud noise, or from other causes such as the side effects of some medications, for many people hearing problems occur with no known cause. Some people notice problems in their 40s and 50s, but the process becomes very noticeable for most people in their 60s and older.

Frisina said that until the biology of the problem is better understood, the best advice for people concerned about hearing loss is to limit exposure to loud, damaging noise and to medications that are toxic to the ears. He also counsels people to eat healthy and to exercise – "all those things you know you should be doing to stay healthy with age," he said.

Meanwhile, his team is looking at the possibility of using gene therapy to try to correct the problem. It may be possible some day to modify a person's inner ear to correct the potassium imbalance that is central to hearing loss. Such an approach might also address the biggest cause of congenital deafness, which involves a genetic mutation that mucks up the potassium balance in the inner ear.

The new findings come from a research group founded by Robert Frisina's father, D. Robert Frisina, Ph.D., founding director of NTID, who heads one of the largest research groups in the world studying age-related hearing loss. The group has attracted top researchers from around the world to come together to study the problem. Members of the group, which numbers more than two dozen, hail from Egypt, Brazil, Russia, China, Korea, India, and the United States.

In addition to Frisina, Frisina and Spencer, the team includes post-doctoral research associate Sherif Tadros, M.D., of both the University and NTID, who is first author of the Hearing Research paper; research nurse Susan Frisina of both NTID and the University; audiologist Frances Mapes of NTID; and otolaryngologist Xiaozia Zhu, M.D., of the University.

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Contact: Tom Ricke ytom_rickey@urmc.rochester.edu 585-275-7954 University of Rochester Medical Center

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Parental Conflict Produces More Than Fleeting Distress for Children

Parental Conflict Produces More Than Fleeting Distress for Children

Six-year-olds whose parents displayed frequent disagreements in their relationship responded to subsequent parental conflicts with elevated distress and negative thoughts, according to a team of researchers from the University of Rochester and the University of Notre Dame.

In the latest issue of the journal Child Development, the team reported examining 223 children twice during a one-year period for their reactions to conflicts between their parents. First, their mothers and fathers participated alone in an exercise in which they attempted to manage and resolve a common point of disagreement. The researchers rated the parents' level of hostility or indifference to capture the characteristic ways that parents managed their conflicts. Then the children observed their parents working through two simulated telephone conversations: a short conflict and a resolution.

Researchers found that the ways parents managed conflicts in the exercise predicted how children responded to the simulated phone conflict—both within a two-week period and one year later. Parents who displayed high levels of discord had children who responded with greater than expected distress to the simulated phone conflict.

"The stressfulness of witnessing several different types of conflict may have long-term implications for children's functioning by directly altering their patterns of responding to those conflicts," says Patrick T. Davies, lead author and professor of psychology at the University of Rochester. "Our results highlight the possibility that several different types of conflict between parents may negatively affect the well-being of children over time," he says.

According to the authors, prior experiences with parental conflicts can alter the way children cope with later conflicts. "Conflict between parents may have distinct meanings and implications for the child and family system even after considering the effects of parenting difficulties," Davies points out.

Although previous work has shown that children don't get used to their parents discord but, instead, become more sensitive to it, Davies and his colleagues wondered if different forms of destructive conflict between parents played different roles in children's reactions. It didn't matter whether the adults disagreed in openly hostile ways or appeared indifferent during the arguments. Both ways of managing conflict were linked with higher than expected distress in children that lasted even one year later.

The primary purpose of the study was to chart stability and change in children's responses to a conflict in the context of interparental and family interactions in the early elementary years. The authors believe that the study lays the foundation for new testing on how children adapt when dealing with interparental conflict.

Co-authors are Melissa L. Sturge-Apple, Marcia Winter, and Deirdre Farrell of the University of Rochester's Department of Clinical and Social Sciences in Psychology at the time of the study, and E. Mark Cummings, professor in the Department of Psychology at the University of Notre Dame. The research was supported by grants and fellowships from the National Institute of Mental Health.

About the University of Rochester: The University of Rochester (rochester.edu) is one of the nation's leading private universities. Located in Rochester, N.Y., the University's environment gives students exceptional opportunities for interdisciplinary study and close collaboration with faculty. Its College of Arts, Sciences, and Engineering is complemented by the Eastman School of Music, Simon School of Business, Warner School of Education, Laboratory for Laser Energetics, and Schools of Medicine and Nursing. PR 2425, MS 863

MEDIA CONTACT: Sharon Dickman (585) 275-4128, sdickman@rochester.edu, February 9, 2006

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