NEW YORK, Mar 22 (Reuters Health) - The sense of smell is among the many everyday functions and senses that deteriorate with Parkinson's disease. But new research into why the sense of smell wanes in Parkinson's patients may lead to ways to improve the problem, according to a report.

New findings published in the March 27th issue of the Proceedings of the National Academy of Sciences suggest that Parkinson's patients have trouble sniffing--or deliberately breathing in a large amount of air. This means helping some patients simply learn to take a big sniff may improve their sense of smell, according to researchers led by Dr. Noam Sobel of the University of California, Berkeley.

Parkinson's disease is a movement disorder that arises when certain brain cells die or become disabled. The major symptoms of this cell loss are muscle stiffness, tremors in the limbs and face, and impaired movement, balance and coordination. Although it may seem to be a minor problem, a weakened sense of smell can dampen patients' appetites and lead to nutritional deficiencies. Until now, researchers had believed that, as with other Parkinson's symptoms, brain-cell death caused the sense of smell to deteriorate.

In the new study, Sobel's team used a series of methods, including scratch-and-sniff tests, to compare the smelling abilities of 20 Parkinson's patients with those of 20 healthy people the same age. The investigators found that the patients had distinct problems with sniffing, which helped to explain their poorer performance in detecting scents.

The researchers next looked at whether they could help Parkinson's patients sniff better by giving them "visual feedback." They had 20 additional patients practice sniffing while watching a computer simulation that showed them when their sniffs were true sniffs.

Of the 20 participants, 18 improved their sniffing ability, but on average it produced only small improvements in their sense of smell, according to the report. However, the half of patients who performed worst on the original sniffing tests did show significant improvements in their sense of smell after having the visual feedback lessons.

While these findings do not imply that sniffing problems are the sole cause of poor smelling ability, the improvements seen in some of these study patients were "striking," according to Sobel's team. For some people with Parkinson's, the authors conclude, a poor sense of smell "may be at least partially reversed."

• More news on Parkinson's Disease

Related MEDLINEplus Pages:

• Parkinson's Disease