MONDAY, March 29, 2004 (HealthDayNews) -- Even modest levels of physical activity, including walking to work and performing household tasks, may reduce a woman's risk for endometrial cancer by as much as 40 percent.
"Patterns of exercise participation were associated with a 35 to 40 percent reduction in endometrial cancer," said study author Charles E. Matthews, who presented his findings Monday at the American Association for Cancer Research's annual meeting in Orlando, Fla. "The public health message is that an active lifestyle, whether from exercise or other domains of your life, confers substantial benefit."
This benefit is apparently not restricted to endometrial cancer, which is cancer of the uterine lining. Two other studies found benefits of physical activity on surviving after breast cancer and on different biomarkers related to cancer survival and risk.
There is increasing evidence that physical activity can reduce the risk of different types of cancer, not to mention heart attacks and stroke, largely because of its effect on decreasing body size. Fat cells contribute to the production of estrogen, which can fuel tumors.
"A woman has estrogen produced by the ovaries but, on top of it, [heavier women] have more peripheral conversion, and unopposed estrogen increases your risk of endometrial cancer," said Dr. Kevin Holcomb, director of gynecologic oncology at Beth Israel Medical Center in New York City.
Matthews and his colleagues analyzed information on 832 women aged 30 through 69, who had been identified through the Shanghai Cancer Registry in China, an area with rapidly rising rates of this cancer. "Endometrial cancer rates have increased by about 75 percent from the early 1970s to the mid-1990s," Matthews, an assistant professor of medicine at Vanderbilt University, said at a teleconference from Orlando. "That's a dramatic increase. The Shanghai Endometrial Cancer Study was initiated in the late 1990s to evaluate the genetic and lifestyle factors that contribute to that increased risk." These women were compared with 846 women living in Shanghai who did not have endometrial cancer.
At in-person interviews, the women were asked about the amount of different physical activities they engaged in, including intentional exercise, walking, cycling for transportation and household chores, during two different time periods -- when they were aged 13 to 19 and for the 10 years prior to the interview.
Women who reported physical activity in both time periods were 30 percent to 40 percent less likely to develop endometrial cancer than women who reported no physical activity in either time period.
Ordinary activities such as walking and taking care of a home reduced risk by about 30 percent. Women who walked for 60 minutes or more each day had a greater risk reduction than those who walked less than 30 minutes. The same held true for women who did four or more hours of housework each day compared to those who did two or fewer hours per day.
"There seemed to be a graded reduction in risk," Matthews explained. "Each increase in activity had a corresponding decrease." Neither biking nor occupational activity seemed to have an effect on risk.
Even heavier women who exerted themselves had a lower risk. "We wanted to know if active heavier women lowered their risk and the results are intriguing," Matthews said. "Among active women at each level of BMI [body mass index], the risk was lower, so there's a suggestion that they may gather some benefit, although this is preliminary."
"This suggests that something other than weight reduction is at play," Holcomb said.
One possibility is that there is a connection with the insulin pathway, Matthews said, though this needs to be explored.
Data on 2,296 women participating in the Nurses' Health Study who had been diagnosed with breast cancer revealed that those who moved more had higher survival rates. The relationship was, again, a graded one, with the risk reduction ranging from 19 percent to 54 percent, depending on the type and length of activity. Even walking for as little as one to three hours a week showed a benefit.
"Physical activity has been shown to improve quality of life for women who have breast cancer, but we conclude that physical activity may also help them live longer as well as live better," said Michelle D. Holmes of Brigham and Women's Hospital and Harvard University in Boston, who was the lead investigator on that study.
A third study presented at the conference found moderately intense exercise reduced the levels of inflammation markers associated with cancer risk and survival. "Moderate exercise lowered markers," said study author Cornelia M. Ulrich, of the Fred Hutchinson Cancer Research Center in Seattle.
More information
The American Cancer Society has more on cancer treatment and exercise and on endometrial cancer.
