WASHINGTON — Breast cancer patients who practice yoga experience lower stress and improved quality of life compared to counterparts who do stretching exercises, a US study indicated.

Researchers at the University of Texas MD Anderson Cancer Center studied 163 women with an average age of 52 who were undergoing radiation therapy for breast cancer, ranging from early onset to stage three.

The women were randomly assigned to one of three groups -- yoga, simple stretching and no instruction in either.

Those assigned to yoga or stretching practiced in one-hour sessions three times a week for the duration of the six-week radiation therapy.

At the end of their radiation treatment, they were asked to report on their own health and well-being at one, three and six months after treatment, and they also underwent tests to measure heart function and stress hormone levels.

Women in the yoga and stretching groups each reported less fatigue than the non-exercise group.

But women who did yoga reported "greater benefits to physical functioning and general health... (and) were more likely to perceive positive life changes from their cancer experience than either other group."

The yoga group also saw the "steepest decline in their cortisol across the day, indicating that yoga had the ability to regulate this stress hormone," the study said.

"This is particularly important because higher stress hormone levels throughout the day, known as a blunted circadian cortisol rhythm, have been linked to worse outcomes in breast cancer."

The study was carried out at US sites, and the yoga practice techniques and instructors were provided by India's largest yoga research institution, Swami Vivekananda Yoga Anusandhana Samsthana in Bangalore.

Lead author Lorenzo Cohen said yoga likely helped patients deal with the transition from cancer treatment back to regular life.

"The transition from active therapy back to everyday life can be very stressful as patients no longer receive the same level of medical care and attention," Cohen said.

"Teaching patients a mind-body technique like yoga as a coping skill can make the transition less difficult."

The researchers are working on a phase III clinical trial to further study how yoga may lead to better physical functioning in breast cancer patients.

A separate study released last month suggested that regular yoga practice by cardiac patients was able to cut irregular heartbeat episodes in half.