(Center for the Advancement of Health) -- Fifteen weeks of tai chi chih practice may have helped a small group of older adults increase the levels of immune cells that help protect their body against the shingles virus, according to a new study.

The report in the September issue of Psychosomatic Medicine is the first study to show that a behavioral intervention can influence the virus-specific immune response, say Michael R. Irwin, M.D., of the Cousins Center for Psychoneuroimmunology at the University of Los Angeles, California and colleagues.

On average, the 18 adults who participated in the tai chi chih program had an increase of nearly 50 percent in immune cell levels one week after completing the program, although individual responses to the exercises varied substantially in this group.

Tai chi chih participants were significantly more likely to increase their immunity than those who did not participate in the program, however.

Tai chi chih practice was also associated with improvements in physical functioning, especially among those who had the most problems with everyday tasks like walking and climbing stairs at the beginning of the study..

Among those participants, tai chi chih's benefits were "comparable or exceeded that reported for hip replacement surgery or for heart valve replacement in older adults," say the researchers.

"However, in light of the small sample, these findings should be cautiously interpreted and viewed as preliminary in nature," Irwin says.

Thirty-six adults, ages 60 and older and living in La Jolla or San Diego, participated in the study. All had either a history of chickenpox or had lived in the United States long enough to assume that they had been exposed to the chickenpox virus, which is similar to the shingles virus.

Exposure spurs the function of immune cells that "remember" the virus and rally the body against reinfection. However, this specific immunity weakens as people age, which may be why older people have higher rates and more severe cases of shingles, Irwin says.

The researchers randomly assigned the adults to tai chi chih instruction or to a waiting list. Those who received the tai chi chih training learned the standard series of 20 "meditation through movement" exercises from an instructor with 20 years' experience. Irwin and colleagues monitored immune levels by through a series of blood tests.

The researchers say that further work is needed to discover whether the effects of tai chi chih on specific immunity are long-lasting, and whether tai chi chih might be useful in boosting the immune response to other infectious diseases.