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Recreational physical activity reduced risk for postmenopausal breast cancer
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Even moderate levels of physical activity may reduce breast cancer risk among postmenopausal women, according to study results.
Agnès Fournier, PhD, of Institut Gustave Roussy in Villejuif, France, and colleagues evaluated data on 59,308 postmenopausal women enrolled in the E3N cohort, a French prospective cohort included within the larger European Prospective Investigation into Cancer and Nutrition. Women were enrolled in the study upon completion of an initial questionnaire sent in 1990.
Agnès Fournier
Follow-up questionnaires were subsequently sent every 2 to 3 years, with the last questionnaire administered in 2005. Diagnoses of breast cancer over the duration of the study were identified through questionnaire self-report or next-of-kin reports.
Researchers collected information on recreational physical exercise through an adapted version of Baecke Questionnaire included as part of the 1993, 1997 and 2002 follow-up surveys. These questions addressed the number of hours per week the women spent walking, cycling, and participating in sports during a typical 2-week period.
The researchers used multivariable Cox proportional hazard models, which included time-varying exposure data on self-reported physical activity, to evaluate the relationship between recreational exercise and invasive breast cancer.
According to study results, women with recreational physical activity levels of 12 metabolic equivalent task-hours per week within the previous 4 years were at lower risk of invasive breast cancer than those with lower levels of activity (HR=0.9; 95% CI, 0.82-0.99).
Dose-response associations did not appear to extend to activity levels beyond 12 task-hours/week.
“Twelve metabolic equivalent task-hour per week corresponds to walking four hours per week or cycling or engaging in other sports two hours per week and it is consistent with the World Cancer Research Fund recommendations of walking at least 30 minutes daily,” Fournier said in a press release. “So, our study shows that it is not necessary to engage in vigorous or very frequent activities; even walking 30 minutes per day is beneficial.”
No significant differences in association were observed between estrogen receptor or progesterone receptor subtypes. These risk associations were consistent regardless of weight change, BMI, waist circumference, or activity levels within less recent (5 to 9 years) time frames.
Women who engaged in physical exercise at 12 task-hours/week levels 5 to 9 years earlier who ceased to maintain this level of activity (less than 12 task-hours per week) were at significantly higher risk for breast cancer compared with those who continued to be active (HR= 1.16; 95% CI, 1.01-1.35). Additionally, women whose activity levels decreased over 5 to 9 years had no decrease in breast cancer risk compared with the least active women at both time points (HR=1.06; 95% CI, 0.87–1.29).
“We found that recreational physical activity, even of modest intensity, seemed to have a rapid impact on breast cancer risk,” Fournier said. “However, the decreased breast cancer risk we found associated with physical activity was attenuated when activity stopped. As a result, postmenopausal women who exercise should be encouraged to continue, and those who do not exercise should consider starting because their risk of breast cancer may decrease rapidly.”
Disclosure: The researchers report no relevant disclosures.
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