These hearing disorders don't just attack the elderly. Kay Sterner, '00, first noticed her hearing loss at age 11. When lying on her right side, she couldn't hear crickets chirping at night. Sterner, 26, has what she describes as "old man hearing" and what doctors call "presbycusis."
Usually presbycusis is an age-related condition where the cells in the ear are thought to wear out. "Hearing loss is associated with grandpas saying, 'Eh?'" says Sterner. "A lot of people joke about it and associate it with old age."
In high school, Sterner wore her first hearing aid-only in one ear and only during class. Today she wears digital hearing aids that are virtually invisible. In face-to-face conversation, her hearing loss is not immediately apparent.
"People have said to me that it's no different than wearing glasses," says Sterner, but she disagrees. "It is much different. This is not something we've completely figured out how to correct. Even with the hearing aids, I don't have normal hearing. I have to wear the hearing aids and I have to ask people to change their behavior for me."
Much of the basic research that may someday help Sterner and others takes place at the UW's Virginia Merrill Bloedel Hearing Research Center. Founded in 1988, the center brings together the research interests of 55 clinical and basic scientists from the School of Medicine, the College of Engineering, and the College of Arts and Sciences. It is one of the largest hearing research collaborations in the country.
The center started with a $5 million gift from Northwest lumber-company magnate Prentice Bloedel during the Campaign for Washington, the UW's first major fund drive. The center honors his wife, Virginia, who suffered from hearing loss. Rubel was the center's first director, and much of its basic research involves hair cell regeneration.
Hair cells are crucial to detecting the vibration of air molecules, what we call "sound." A vibration may be produced, for instance, by a bow on a violin string or a person's voice. Hearing begins when the air disturbance impinges on the eardrums, deep in each ear canal. The eardrum is attached to a series of three, tiny, middle-ear bones whose movements are transmitted to the cochlea, a snail-shaped organ about the size of a pea, located in the skull behind the eye. Fluid inside the cochlea is moved by the actions of the middle ear bones.
Photo by Kathy Sauber
Within the cochlea are 15,000-16,000 hair cells, so called because under a powerful microscope protrusions on the cells resemble hairs-but they have no relation to the hairs on your head. In the inner ear, these groups of small "hairs" bend and yield according to the movement of fluid in the cochlea, much like reeds in the current of a river. The movement of the hairs generates neural signals, which are carried to the brain. Highly complex combinations of neural signals are interpreted by the brain as, perhaps, Beethoven's Ninth Symphony or Mom on the other end of the telephone.
In humans, hair cells come in four rows within the cochlea. There are inner hair cells and outer hair cells. Inner hair cells detect sound. The outer hair cells are still a bit of a mystery, but they seem to strengthen sound by amplifying the response of inner hair cells. Outer hair cells are the most vulnerable to drugs, excessive noise and aging. When they wear out and die, a hearing aid may act as an amplifier to boost the sound signals-but without the precision of the original cells.
"If the inner hair cells die, you're deaf," explains George Gates, an otolaryngology professor and current director of the Bloedel Center. "But hearing aids supplement the function of outer hair cells by making sounds louder. Hearing aids are an extra power source. You are putting acoustic energy into the ear."
One important question, according to Gates and Rubel, is why do adults lose hearing as they age? Scientists think there is a combination of causes involving genetics, cellular biology and biochemistry. Much of the effort is focused on genetics, although no one would say that gene therapy is a viable option, yet. "Gene therapy is a long and rugged road to explore," says Gates.