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The findings support past studies that found health benefits related to the traditional Chinese exercise.

"It combines slow motion exercise and mind concentration to focus on movement. That itself can reduce your stress and, of course, it will increase your flexibility and endurance," said Dr. Xianglan Zhang, one of the study's authors from the Vanderbilt University School of Medicine in Nashville, Tennessee.

Zhang said her study could not prove, however, that tai chi was responsible for some men's longer lifespan.

Earlier research has shown tai chi can be beneficial for people with chronic conditions, for example by improving balance among those with Parkinson's disease (see Reuters Health report of February 8, 2012 here: reut.rs/xtA2xa).

To see whether tai chi and other forms of exercise might influence lifespan, Zhang and her colleagues looked to a large study of middle aged and elderly men in Shanghai.

More than 61,000 men participated in the study. Researchers tracked their health and lifestyle for more than five years.

Close to 22,000 participants reported that they exercised at least once a week, and the rest were considered non-exercisers.

Over the course of the study, 2,421 men died, including 3.3 percent of the non-exercisers and 5.1 percent of the men who exercised.

Exercisers tended to be older and more of them had heart disease and diabetes.

After Zhang's group took into account men's age, health conditions and whether they smoked, exercise was tied to a 20 percent lower likelihood of dying.

Similarly, 6.2 percent of the close to 10,000 men who practiced tai chi died during the study, but after accounting for other risk factors, the researchers found they were 20 percent less likely to die than men who didn't exercise.

Men who walked regularly were 23 percent less likely to die during the study, and men who jogged were 27 percent less likely to die, Zhang's team reports in the American Journal of Epidemiology.

Dr. Chenchen Wang, director of the Center for Complementary and Integrative Medicine at Tufts Medical Center in Boston, said that because Zhang's study was observational, and did not randomly assign people to practice tai chi or not, it's impossible to say whether the exercise itself is responsible for the findings.

There's always the possibility, for instance, that people who choose tai chi tend to have healthier lifestyles.

But Wang, who wasn't involved in the new study, told Reuters Health the results are interesting, and "they provide a very important foundation for future research."

Zhang said the findings support tai chi as a healthy activity.

"I think for the elderly people, especially to maintain flexibility and balance, this is a good option for people to consider," Zhang told Reuters Health.

SOURCE: bit.ly/1aImEF3 American Journal of Epidemiology, online June 27, 2013.