November 11, 2010 (Philadelphia, Pennsylvania) — Women who exercise for at least 150 minutes a week might have a reduced risk for endometrial cancer, according to a study presented here at the Ninth Annual American Association for Cancer Research (AACR) International Conference on Frontiers in Cancer Prevention Research.
Exercise cuts the risk even for women who overweight, said Hannah Arem, a doctoral candidate at the Yale School of Public Health in New Haven, Connecticut. She spoke during a press conference at the meeting.
This is important in light of the fact that body mass index (BMI) "is one of the major risk factors for endometrial cancer," she explained.
The exercise that counted in the study's tallies was "moderate- to vigorous-intensity sports/recreational physical activity."
"Does vigorous walking at conferences count?" asked Judy Garber, MD, MPH, director of the Center for Cancer Genetics and Prevention at the Dana-Farber Cancer Institute, Boston, Massachusetts, and president-elect of the AACR. Dr. Garber moderated the press conference and self-reported quite a bit of walking around the Philadelphia Convention Center.
Dr. Garber's humor implicitly hinted at a challenge in the findings: that working out 5 days a week for 30 minutes is a tall order for many busy professionals.
Ms. Arem noted that exercise 5 days a week for 30 minutes at a time is a standard recommendation, and that the effectiveness of other workout regimens is not known.
The study contributes to the literature on exercise and endometrial cancer, which is the fourth most common cancer among women in the United States.
Although it adds supports the link between physical activity and lower risk for endometrial cancer, other research has shown conflicting results, said Ms. Arem. However, many other studies have not reported on the reliability or validity of physical activity questionnaires.
In addition, few studies have examined the combination of physical activity and BMI on endometrial cancer risk. This study looked at these variables independently and in combination.
Hormone and lifestyle factors explain up to 80% of risk for endometrial cancer, Ms. Arem said.
Exercise Cuts Risk, Even for the Overweight
Ms. Arem and colleagues examined data collected from a case–control study led by Herbert Yu, MD, PhD, associate professor at the Yale School of Public Health. The study compared 668 women who had endometrial cancer with 665 age-matched control women.
The study involved a questionnaire that collected data on physical activity levels in 29 different kinds of activities in the 2 to 5 years before the diagnosis of endometrial cancer, said Ms. Arem.
As is typical in exercise studies, the activity was converted to metabolic equivalents (METs), which correspond to the intensity of exercise and allow for easier comparative analysis.
After adjustment for age, BMI, and other risk factors, the investigators found that the risk for endometrial cancer in women exercising 7.5 MET hours per week (about 150 minutes of moderate to vigorous activity) was 34% lower than the risk women for who did not exercise at all.
The investigators found that women who were normal weight and active had a reduction in risk of 73%, compared with inactive women who were overweight (BMI above 25 kg/m2).
Women who were normal weight but inactive had a 55% lower risk for endometrial cancer than inactive women who were overweight. Women who were overweight but active had a 38% lower risk for endometrial cancer.
In summary, risk reduction occurred in all women who exercised at the study's required threshold, regardless of their weight. "Exercise is an important public health intervention for women at risk of endometrial cancer," said Ms. Arem.
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