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CHICAGO -- Gentle stretching, breathing, and other exercises in a regular yoga program may ease sleep and fatigue problems common among cancer survivors, a randomized trial found.

Sleep quality rose 22% after just four weeks of yoga, a benefit significant at P<0.05 compared with the 12% improvement from baseline on usual care, reported Karen Mustian, PhD, MPH, University of Rochester Medical Center in Rochester, N.Y., and colleagues.

Yoga had an even greater effect on fatigue, with a 42% reduction among yoga participants versus 12% among controls (P<0.05), she said at a press conference in advance of her presentation at the American Society of Clinical Oncology meeting here.

Similar yoga classes done in the community would also likely fight these side effects, which affect the majority of cancer survivors, Mustian noted.

Kathryn Schmitz, PhD, MPH, FACSM, of the, University of Pennsylvania School of Medicine, said that the concept of recommending yoga or any exercise is still a novel one for many in the cancer community, who for years were likely to regard cancer survivors as poor candidates for an exercise intervention. Schmitz was not involved in the study, but offered her comments in response to an ABC/番茄社区 query.

Even now, she said, clinicians typically advise cancer patients to "take it easy."

"What we conclude based on a really thorough review of [yoga programs] is that it is absolutely safe for cancer survivors during and post treatment to be physically active, and indeed there are tremendous benefits to doing so."

ASCO president Douglas W. Blayney, MD, of the University of Michigan in Ann Arbor, agreed that the results are "readily applicable" for a huge patient population.

"This emphasizes the increasing importance of ameliorating complications of therapy in long-term cancer survivors," he said at the press conference. "There are literally millions of patients to whom it might be applicable in the U.S."

Yoga isn't the only form of exercise to show benefits for cancer survivors.

Walking programs and resistance training, for example, are considered to be excellent behavioral options to counteract fatigue in particular, Mustian said at the press conference.

Although there haven't been any head-to-head studies to suggest which type of exercise is most effective, yoga may have some advantages beyond just getting patients moving, Mustian speculated.

Small studies have suggested that the deep breathing training and mindfulness aspects of yoga may help regulate parasympathetic nervous system activity and the hypothalamic-pituitary-adrenal axis, she explained.

Her group's phase II/III trial included 410 survivors of early stage cancers (96% women, 75% breast cancers) from nine community clinical oncology centers who reported at least moderate problems with sleep in the two to 24 months after finishing adjuvant cancer therapy.

They were randomized to standard care monitoring alone or with a four-week yoga program with 75-minute sessions twice weekly.

At baseline, 83% to 84% of patients met the clinical cutoff criteria for impaired sleep quality with a Pittsburgh Sleep Quality Index score over 5. But by the end of the trial, 31% of yoga participants had recovered compared with the 16% of control group patients who saw scores drop below 5 (P<0.05).

This advantage came despite a comparative drop in use of sleeping pills among yoga participants (-21% versus +5%, P<0.05).

Other findings included significantly less daytime sleepiness after the yoga program (-29% versus -5% from baseline, P<0.05) and a 6% mean improvement in quality of life score among yoga participants compared with no change in the control group (P<0.05).

The researchers tested a program designed for cancer survivors (UR Yoga for Cancer Survivors, YOCAS®) that included only gentle yoga postures in standing, seated, transitional, and lying-down positions along with breathing exercises, meditation, and visualization.

These components can be found in typical Hatha or restorative yoga classes in communities across the country, Mustian said.

However, she cautioned that the results may not generalize to more rigorous or heated forms of yoga in cancer survivors.

"It's important for folks to know that not all yoga is the same, may not provide the same benefits, and may or may not be safe," Mustian said in an interview with ABC News.

Michael Irwin, MD, a professor of psychiatry and biobehavioral science at UCLA's David Geffen School of Medicine, also cautioned, in an e-mail, that the study findings are probably not enough on which to make solid clinical recommendations.

He pointed out, for example, that this was a short-term study. He said he would really like to see data about long-term effects.

This article was developed in collaboration with ABC News.

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