Hearing loss has been linked with a variety of medical, social and cognitive ills, including dementia. However, a new study led by a Johns Hopkins researcher suggests that hearing loss may also be a risk factor for another huge public health problem: falls. The finding could help researchers develop new ways to prevent falls, especially in the elderly, and their resulting injuries that generate billions in health care costs in the United States each year, by some estimates. To determine whether hearing loss and falling are connected, Frank Lin, M.D., Ph.D., at Johns Hopkins, and his colleague Luigi Ferrucci, M.D., Ph.D., of the National Institute on Aging, used data from the 2001 to 2004 cycles of the National Health and Nutrition Examination Survey. This research program has periodically gathered health data from thousands of Americans since 1971.
Yale scientists have discovered the molecular pathway by which maternally inherited deafness appears to occur: Mitochondrial DNA mutations trigger a signaling cascade, resulting in programmed cell death. The study is in Cell. Mitochondria are cellular structures that function as "cellular power plants" because they generate most of the cell's supply of energy. They contain DNA inherited from one's mother. Mitochondria determine whether a cell lives or dies via the process of programmed cell death, or apoptosis. The Yale scientists focused on a specific mitochondrial DNA mutation that causes maternally inherited deafness. The mutation occurs in a gene that codes for RNA in mitochondrial ribosomes, which generate proteins required for cellular respiration. The team found that cell lines containing this mutation are prone to cell death not directly due to the mutation, but rather because it enhanced a normal chemical modification of the RNA called methylation, which regulates ribosome assembly.
Cochlear implants may be a safe, effective option for some organ transplant patients who've lost their hearing as an unfortunate consequence of their transplant-related drug regime, researchers report. The antibiotics and immunosuppressive drugs required by organ transplant patients can cause deafness, said Dr. Brian J. McKinnon, otologist and neurotologist at the Medical College of Georgia at Georgia Health Sciences University. Antibiotics can destroy the finite number of dark cells in the inner ear. These cells produce the minute amount of fluid needed to help convert sound waves to neural impulses the brain can interpret. Apparently these dark cells are very metabolically active and antibiotics are designed to interfere with bacteria's metabolic activity. "When you destroy the ability to make fluid, the system no longer functions, " McKinnon said.
Though an estimated 26.7 million Americans age 50 and older have hearing loss, only about one in seven uses a hearing aid, according to a new study led by Johns Hopkins researchers. The finding adds clarity to less rigorous estimates by device manufacturers and demonstrates how widespread undertreatment of hearing loss is in the United States, the study investigators say. "Understanding current rates of hearing loss treatment is important, as evidence is beginning to surface that hearing loss is associated with poorer cognitive functioning and the risk of dementia, " says study senior investigator, otologist and epidemiologist Frank Lin, M.D., Ph.D. "Previous studies that have attempted to estimate hearing aid use have relied on industry marketing data or focused on specific groups that don't represent a true sample of the United States population, " adds Lin, an assistant professor at the Johns Hopkins University School of Medicine and the university's Bloomberg School of Public Health.
Noise Exposure Can Cause Long-Lasting Changes To Sensory Pathways; Touch-Sensing Nerve Cells May Lead To Future Tinnitus Treatments
We all know that it can take a little while for our hearing to bounce back after listening to our iPods too loud or attending a raucous concert. But new research at the University of Michigan Health System suggests over-exposure to noise can actually cause more lasting changes to our auditory circuitry - changes that may lead to tinnitus, commonly known as ringing in the ears. U-M researchers previously demonstrated that after hearing damage, touch-sensing "somatosensory" nerves in the face and neck can become overactive, seeming to overcompensate for the loss of auditory input in a way the brain interprets - or "hears" - as noise that isn't really there. The new study, which appears in The Journal of Neuroscience, found that somatosensory neurons maintain a high level of activity following exposure to loud noise, even after hearing itself returns to normal.