Consistent Exercise Linked to Lower Risk for Death From Colon Cancer

Fran Lowry

January 07, 2011

January 7, 2011 — Add another study to the body of literature that says exercise is good for you, especially with regard to modifying cancer risk and outcomes.

The latest research, carried out by at the Siteman Cancer Center at Washington University School of Medicine and Barnes-Jewish Hospital in St. Louis, Missouri, shows that regular long-term physical activity is associated with a lower risk for colon cancer mortality.

The study appears in the December issue of Cancer Epidemiology, Biomarkers & Prevention.

"This study is among the first to show that physical activity can make the disease less deadly," lead author Kathleen Y. Wolin, ScD, told Medscape Medical News. "It supports an existing body of research that suggests that physically active lifestyles have a host of benefits, both for cancer prevention and cancer-related death."

However, an expert not involved in this research who was approached for comment said the study was negative, because it fails to show that exercise reduces the risk of getting colon cancer.

Previous Studies

There is already a body of literature showing the benefits of exercise on both physical and mental well-being, including several studies showing a reduction in the risk for cancer, as reported recently by Medscape Medical News.

In November 2010, it was reported that women who exercised for at least 150 minutes a week might have a reduced risk for endometrial and postmenopausal breast cancer.

In addition, new guidelines from the American College of Sports Medicine highlighted the benefits to cancer patients of exercise training both during and after cancer treatments to improve physical functioning, quality of life, and cancer-related fatigue.

Effect on Colon Cancer

In the latest study, Dr. Wolin and her colleagues sought to examine whether changes in physical activity alter the risk for colon cancer incidence and mortality.

"We know people will be active when they are younger, but then work or family obligations get in the way, and they tend to become less active. Others may not have been that active in young adulthood, but then in their 30s or 40s, when the pounds start creeping on, or when they start to be more concerned about their health and wanting to live longer, they become physically active," Dr. Wolin explained. "In this study, we were able to look at people's behaviors at multiple time points."

The researchers used data from the American Cancer Society Cancer Prevention Study II (CPS-II) Nutrition Cohort to look at whether changes in physical activity influenced either the incidence of colon cancer diagnosis or the risk for death from the disease.

CPS-II comprised more than 150,000 men and women. To determine how exercise affected colon cancer, the researchers compared levels of physical activity between 1982 and 1997, and linked those activity levels to the number of colon cancer diagnoses between 1998 and 2005 and to the number of colon cancer deaths that occurred between 1998 and 2006.

Physical activity included walking, jogging/running, lap swimming, tennis, racquetball, bicycling, stationary biking, aerobics/calisthenics, and dancing.

The study found that people who were consistently active for at least 10 years had a significantly lower risk of dying from their colon cancer than those who were consistently inactive (multivariable hazard ratio, 0.45; 95% confidence interval, 0.34 to 0.59). This held after adjustment for body mass index.

People who were consistently active over 15 years had half the risk for colon cancer death as those who were more sedentary. However, being physically active did not appear to reduce their risk of getting colon cancer, Dr. Wolin said.

"Regular long-term physical activity was associated with a lower risk of colon cancer mortality," she said. "People often wonder around the start of a new year whether exercise really will help them stay healthy or whether it's already too late. It's never too late to start exercising, but it's also never too early to start being active. That's the message we hope people will take away from this study."

A Negative Study That Fails to Show That Exercise Reduces Risk

Asked to comment on this study for Medscape Medical News, Susan G. Fisher, MS, PhD, professor and chair of the Department of Community and Preventive Medicine at the University of Rochester in New York, said that it was well done, but because the data were not collected prospectively, it has limitations.

"It's a negative study. It fails to show that increasing physical activity over a 10- to 15-year period reduces an individual's risk of developing colon cancer," she said. "While this study does suggest that individuals who consistently participate in vigorous regular exercise throughout adulthood are less likely to die from colon cancer, the risk of developing colon cancer does not appear to be reduced," she said.

Because these results are extracted from data that were previously collected, there are potential limitations in the methods used to measure the amount of physical exercise over a 10- to 15-year period, Dr. Fisher added. "These measurement difficulties may alter the study results. For instance, if I exercised 3 or 4 times a week and developed colon cancer, it's not unreasonable to think I would begin to have some symptoms, some indigestion or maybe fatigue, even before my diagnosis, and I would end up decreasing my exercise program. So people may be decreasing their exercise because they're feeling sick; I don't think they controlled for that perfectly," she said.

Dr. Wolin and Dr. Fisher have disclosed no relevant financial relationships.

Cancer Epidemiol Biomarkers Prev. 2010;19:3000-3004. Abstract

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