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Studies show importance of oral health in older population (10/8/97)

Children probably think about saliva more than adults do, but neither children nor adults realize the importance of saliva to general health.

As the body ages, the flow of saliva decreases and sometimes stops altogether. Without this clear, alkaline secretion, food would have no taste, speech would be affected and overall health would deteriorate. In addition, saliva contains an enzyme that moistens, softens and helps digest food, as well as mucins that help keep the teeth and mouth moist and aid in swallowing.

The study of saliva is one section of a four-part investigation into aging and oral health, sponsored by a National Institute of Dental Research (NIDR) grant, being conducted by a group of scientists at the University of Texas Health Science Center at San Antonio. Co-principal investigators are Chih-Ko Yeh, DDS, PhD, assistant professor in dental diagnostic science and research dentist with the Geriatric Research, Education and Clinical Center of the South Texas Veterans Health Care System; Michael Dodds, PhD, director of the Salivary Function Clinic and an associate professor; and Dorthea Johnson, MS, director of the Sialochemistry Laboratory and research associate professor, both in the department of community dentistry. These researchers are studying the importance of saliva in maintaining good health in the aging population.

"Saliva, with its antimicrobial and antifungal agents, is an important factor in maintaining a healthy mouth and gums," Ms. Johnson said. "There are some diseases such as Sjogren's syndrome, or disease treatments such as radiation therapy to the head and neck, that impair salivary gland function. This reduction in saliva puts these individuals at increased risk for dental disease."

"We take saliva for granted," Dr. Yeh said, "but when this natural function stops, either because of aging or disease, the quality of life drastically diminishes."

Dry mouth is more common than might be expected. Approximately thirty percent of one study group stated that their mouths usually felt dry and about half of those, or fifteen percent, had abnormally low salivary flow rates. Clearly, this is a common problem.

"If people aren't able to chew well, the amount of saliva decreases," Dr. Dodds said. "Although drugs sometimes stimulate saliva flow they could have the opposite effect--in certain cases, saliva flow diminishes. Some people use hard candy to stimulate flow, but this promotes cavities."

"When patients with head or neck cancer take chemotherapy, their salivary glands shrink. This causes dry mouth," Dr. Dodds said. "These patients often say if they had known that chemotherapy was going to create this problem (lack of saliva), they would have preferred the cancer. This statement is evidence of the misery this condition causes."

"Saliva flow decreases significantly with age and the decrease is greater in females than in males," Ms. Johnson said. "In women, an abrupt decrease occurs during menopause. According to our research, the flow rate is slightly higher in women taking estrogen replacement, suggesting hormonal changes may affect saliva flow."

The researchers are utilizing 1,100 community residents of the San Antonio area who are 35 years of age or older, noting differences in the saliva flow between the male and female aging population, and characterizing the composition of saliva as well as its bactericidal activities. One major antimicrobial protein in saliva, lysozyme, is capable of destroying some bacteria. It has a dose- and time-dependent killing effect on candida, a yeast-like fungus. The research group found that individuals with high oral candida counts had an increase in lysozyme concentrations, suggesting saliva affords the body natural protection against disease.

Other NIH sponsored studies within the laboratory include an analysis of saliva collected from patients with Sjogren's Syndrome and HIV-infected patients. The HIV study is carried out with the Henry M. Jackson Foundation at Wilford Hall Medical Center.

The Health Science Center's Salivary Function Clinic and Sialochemistry Laboratory are among the most complete in the nation. In addition to the three National Institutes of Health studies currently being conducted, the Sialochemistry Laboratory, begun in 1986, is initiating collaborative studies with other investigators within the Health Science Center.

Contact: Jan Elkins (210) 567-2570