Nervous System Imbalance May Cause Fatigue in Breast Cancer Survivors

The persistent fatigue and exhaustion plaguing some breast cancer survivors after successful treatment stems from a tug of war between the "fight-or-flight" and "resting" parts of the autonomic nervous system, with the former working overtime and the other unable to rein it in, a new study suggests. Researchers from Ohio State University split 109 women who had completed breast cancer treatment up to two years earlier into two groups those who did and didn't report long-term fatigue and tested their blood for a baseline level of norepinephrine, a stress hormone. Participants were then asked to give a five-minute speech and do a series of verbal math problems, both tasks aimed at increasing their stress levels.

As expected, further blood tests showed that levels of norepinephrine associated with the "fight-or-flight" sympathetic nervous system rose in both groups after the stressful experience, researchers said. However, breast cancer survivors who experienced persistent fatigue had higher levels than those who weren't chronically tired. The study, released online in advance of publication in an upcoming print issue of the journal Psychoneuroendocrinology, was partially funded by the U.S. National Institutes of Health and the American Cancer Society.

The findings are the most recent from a 30-year-long study about the effects of stress on the human body. The researchers used earlier data from a larger ongoing study looking at whether yoga can ward off continuing fatigue in breast cancer patients. "We're not sure if the fatigue is stress-induced. But certainly cancer is an extremely stressful life event," said study author Christopher Fagundes, a postdoctoral fellow at Ohio State University's Institute of Behavioral Medicine Research. "So those stressors might be contributing to those autonomic system changes."