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Research of hearing loss has been difficult over the years.  New research is tracking how premature infants lose hearing, and how it can be prevented.  This knowledge could have broader application to adults.

Both humans and mice are particularly vulnerable to noise- and drug-induced hearing loss at young ages.

Sound levels measured by Clark and Weathers showed that premature infants being airlifted tested were exposed to almost 100 decibels for a period of 12 minutes before takeoff, similar to a lawn mower or chain saw. These levels could be especially damaging to premature babies.

"The laboratory mouse is a well-established model for human hearing," says coauthor Kevin K. Ohlemiller, Ph.D., research associate professor of otolaryngology. "They possess similar inner ear anatomy and physiology and similar patterns of age-related, noise-induced and drug-related hearing loss."

Ohlemiller worked with Elizabeth A. Fernandez, then a doctoral student in the Program in Audiology and Communication Sciences, to see if loud noise and a low dose of kanamycin would exacerbate each other's effects. Because the first month of life is when mice are most vulnerable to noise and drugs that damage hearing, 20- to 30-day old mice were injected with either kanamycin or saline solution twice a day for 11 days. They were then exposed to 110 decibels of noise for 30 seconds.

Two surprising findings arose.

First, this particular strain of mice was very sensitive to noise-induced hearing loss. Significant loss of some sensory cells in the ear resulted in permanent hearing damage, even over the short time span.

Second, a regular, low dose of kanamycin completely protected the mice against this sensory cell damage and hearing loss. The protective effect of repeated doses persists for at least two days after the last injection, the scientists noted.

Researchers plan to use these hearing research findings in a number of ways.

They can map the genes in this strain of mice to determine what makes them so noise-sensitive and possibly figure out how kanamycin protects sensory cells in the ear.

In addition, the findings open up new possibilities for clinical research.

Learning how kanamycin protects the ear's sensory cells could help scientists develop drugs with similar effects. Medications that protect the ears from damaging noise levels could benefit a wide range of groups, from soldiers to airline workers to premature babies.

Basic Science Research PLUS Clinical Problem & Practice

"This very dramatically points out the benefits of having basic scientists who can take a clinical problem and find a result opposite of what we expected," Clark says. "These results not only energize laboratory scientists and begin new lines of research, but they also have implications for clinical practice. This has been an amazing sequence of events, to start a project in a helicopter and end up under a microscope."

Fernandez EA, Ohlemiller KK, Gagnon PM, Clark WW. Protection against noise-induced hearing loss in young CBA/J mice by low-dose kanamycin. Journal of the Association for Research in Otolaryngology. Jan. 22, 2010 (advance online publication).

Funding from National Institutes of Health and the Washington University School of Medicine in St. Louis Department of Otolaryngology supported this research.

Heavy backpacks place a measurable strain on the spines of children, with heavier loads causing greater spinal strain and increased back pain, reports a study in Spine, January 2010 

My husband and I started getting concerned about heavy backpacks when our son was required to carry a very heavy backpack weighted down with a year's worth of books when he was in gradeschool.  It just didn't make sense.  It's taken a long time to get the research to prove the problems.  But it's here now, and solutions need to be found -- such as eBook readers.

The next step in convincing schools to "lighten the load" is to show how expensive back pain and back care is to our society.  Maybe business and government can prevent that long term impact on healthcare costs by providing children is an alternative to heavy books.

Test Results for Children's Back Health 

Magnetic resonance imaging (MRI) scans show compression of the spinal discs and spinal curvature caused by typical school backpack loads in children, according to Dr. Timothy Neuschwander of University of California, San Diego, and colleagues.

Backpacks' Effects on Disc Height and Spinal Curve Linked to Back Pain

The study included eight children, mean age 11 years. A special upright MRI scanner was used to image the children's spines in standing position--first with an empty backpack, then with increasing weights of 9, 18, and 26 lb. These weights represented about 10, 20, and 30 percent of the children's body weight.

Two key spinal measurements changed as the backpack load increased.

• Heavier weights caused compression of the intervertebral discs, which act as a cushion between the vertebrae (bones of the spine).
  
• Especially in the lower spine, the disc height became smaller (reflecting greater disc compression) at heavier backpack weights.
• Heavier loads were also associated with increased curvature of the lower spine, either to the right or the left.
  

Half of the children had a significant spinal curve even with the 18 lb weight. Most of the children had to adjust their posture to bear the 26 lb backpack load.

As backpack weight increased, so did the amount of pain reported by the children. At the heaviest load, the average pain score was nearly five (on a ten-point scale).

Parents are increasingly concerned about the heavy backpacks their children have to carry. The new study is the first to use imaging techniques to see how backpacks affect children's spines.

More than 90 percent of U.S. children carry backpacks, typically with weights equal to 10 to 22 percent of their body weight.

Carry Backpacks on One Shoulder or Two?

The results suggest that heavy backpacks cause compression of the spinal disks and increased spinal curvature, both of which are related to back pain reported by the children. Although the children were wearing the backpack straps over both shoulders when the MRI scans were performed, the researchers note that spinal curvature could be even greater if the backpack was carried over one shoulder--as many children do.

Lower Back Pain for Children -- Through Adulthood

"Low back pain in children may be worsened by discogenic [disc-related] or postural changes," Dr. Neuschwander and colleagues write. This could have long-term implications, as children with back pain are at increased risk of having back pain as adults. The researchers call for similar studies to examine the effects of heavy backpacks in children with existing back pain.

About Spine
Recognized internationally as the leading journal in its field, Spine is an international, peer-reviewed, bi-weekly periodical that considers for publication original articles in the field of spine. It is the leading subspecialty journal for the treatment of spinal disorders. Only original papers are considered for publication with the understanding that they are contributed solely to Spine. According to the latest ISI Science Citation Impact Factor, Spine ranks highest among subspecialty orthopedic titles. Visit the journal website at www.spinejournal.com

Each year, approximately 5,000 fatal work-related injuries and 4 million non-fatal injuries and illnesses occur in the United States. This number represents both unnecessary human suffering and high economic costs.  .

Committee on the Review of NIOSH Research Programs; Institute of Medicine and National Research Council Authoring Organizations