MONDAY, Dec. 8, 2014 (HealthDay News) -- Watching too much television may lower your chances of survival after colon cancer, new research suggests.
"The take-away message from our study is that both minimizing TV viewing, to less than two hours per day, and increasing exercise, to four-plus hours per week, were associated with lower mortality risk among colorectal cancer survivors," explained study author Hannah Arem, a postdoctoral fellow with the U.S. National Cancer Institute's nutritional epidemiological branch.
While the study showed an association between television watching, exercising and survival odds among colon cancer patients, it did not prove a cause-and-effect link.
Arem and her colleagues report their findings online Dec. 8 in the Journal of Clinical Oncology.
To explore the impact of lifestyle on colon cancer survival, the study authors sifted through data that had been collected by the U.S. National Institutes of Health for an earlier study.
The initial investigation had included more than 566,000 men and women between the ages of 50 and 71, all of whom had completed an initial health and lifestyle questionnaire at some point between 1995 and 1996.
All were asked to indicate the degree to which they had routinely participated in moderate to vigorous "leisure-time activity" on a weekly basis over the past decade. Activities included swimming, biking, golf, tennis, dancing, fast-walking, jogging, aerobic exercise and/or heavy gardening.
The new analysis honed in on the nearly 3,800 participants who went on to be diagnosed with colon cancer. On average, the diagnoses had occurred approximately five years following completion of the initial survey.
By stacking pre-diagnosis exercise habits up against cancer survival information, the researchers determined that colon cancer patients who had seven or more hours of weekly leisure activity before their diagnosis showed a 20 percent lower risk of dying -- for any reason -- than those who had engaged in no leisure activity whatsoever.
And after analyzing a follow-up survey completed between 2004 and 2005 by roughly 1,800 of the original 3,800 colon cancer patients, the team found that those who engaged in seven or more hours of weekly leisure activity post-diagnosis faced a 31 percent lower risk of dying from any cause, regardless of their activity levels before diagnosis.
The study team also found that those patients who routinely watched no more than two hours of TV per week before diagnosis faced a 22 percent lower risk of dying from any cause than those who watched five or more hours per week.
Television viewing was chosen as a stand-in for sedentary behavior "because it is the most prevalent leisure-time sedentary behavior," Arem said.
The research team found a lower mortality risk among those who watched less TV post-diagnosis, although it was not deemed statistically significant.
On the more specific question of how exercise habits and television viewing routines might affect the risk of dying from colon cancer, Arem said the research team could not draw any firm conclusions.
"We looked at both all-cause mortality and colorectal cancer-specific mortality in these analyses," she noted. "[And] the risk of dying from colorectal cancer was higher among the individuals who watched more TV compared to those who watched less than two hours per day, but the associations were not statistically significant."
The team nevertheless concluded that when dealing with colon cancer patients, doctors may want to stress the potential benefits associated with increased activity on the one hand, and minimal television watching on the other.
Dr. Andrew Chan, an associate professor in the department of medicine at Harvard Medical School, said the findings highlight the strong link between lifestyle choices and health.
"We are becoming more and more aware of the importance of lifestyle in really determining how someone is going to do after they've been diagnosed with cancer," he noted. "And it's time that patients come to understand that, in general, being more physically active is important to maintaining one's health."
"Now, of course, lifestyle is important no matter who you are, even for individuals who don't have a history of cancer," added Chan, who is an associate professor of medicine and gastroenterology at Massachusetts General Hospital in Boston. "But certainly for cancer survivors specifically, this study drives home the point that an active lifestyle can be critical, both for maintaining overall health and preventing the recurrence of disease."
Visit the U.S. National Institutes of Health for more on colon cancer.
SOURCES: Hannah Arem, M.H.S., Ph.D., postdoctoral fellow, nutritional epidemiological branch, U.S. National Cancer Institute, Rockville, Md.; Andrew Chan, M.D., M.P.H., associate professor, department of medicine, Harvard Medical School, and associate professor, medicine and gastroenterology, Massachusetts General Hospital, Boston; Dec. 8, 2014, Journal of Clinical Oncology, online
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