Physical activity is inversely related to breast cancer risk

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Physical activity is inversely related to breast cancer risk among black and white women.

According to investigators in the United States, "Physical inactivity is a potentially modifiable breast cancer risk factor. Because few data on this relationship exist for black women, we examined the relationship between breast cancer risk and lifetime and time- or age-specific measures of recreational exercise activity among white women and among black women."

L. Bernstein and colleagues explained, "The Women's Contraceptive and Reproductive Experiences Study was a multicenter population-based case-control study of black women and white women aged 35-64 years with newly diagnosed invasive breast cancer. We collected detailed histories of lifetime recreational exercise activity during in-person interviews with 4,538 case patients with breast cancer (1,605 black and 2,933 white) and 4,649 control subjects (1646 black and 3,033 white)."

"Control subjects were frequency-matched to case patients on age, race, and study site," stated the researchers. "We examined associations between exercise activity measures (metabolic equivalents of energy expenditure [MET]-hours per week per year) and breast cancer risk overall and among subgroups defined by race, other breast cancer risk factors, and tumor characteristics by use of unconditional logistic regression. All statistical tests were two-sided."

"Among all women, decreased breast cancer risk was associated with increased levels of lifetime exercise activity (e.g., average MET-hours per week per year, Ptrend=.002). An average annual lifetime exercise activity that was greater than the median level for active control subjects was associated with an approximately 20% lower risk of breast cancer, compared with that for inactivity (for 6.7-15.1 MET-hours/week/year, odds ratio [OR]=0.82, 95% confidence interval [CI]=0.71 to 0.93; for greater than or equal to15.2 MET-hours/week/year, OR=0.80, 95% CI=0.70 to 0.92)," the researchers reported.

"The inverse associations did not differ between black and white women (for MET-hours/week/year, Ptrend=.003 and Ptrend=.09, respectively; homogeneity of trends p=.16)," the study group recorded. "No modification of risk was observed by disease stage, estrogen receptor status, or any breast cancer risk factor other than first-degree family history of breast cancer."

The authors concluded, "This study supports an inverse association between physical activity and breast cancer among black women and among white women."

Bernstein and colleagues published the results of their research in the Journal of the National Cancer Institute (Lifetime recreational exercise activity and breast cancer risk among black women and white women. J Natl Cancer Inst, 2005;97(22):1671-1679).

For additional information, contact L. Bernstein, Department of Preventive Medicine, Keck School of Medicine, USC/Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA; E-mail: lbern@usc.edu.

The publisher of the Journal of the National Cancer Institute can be contacted at: Oxford University Press Inc., Journals Dept., 2001 Evans Road, Cary, NC 27513, USA.

Keywords: Los Angeles, California, United States, Breast Cancer, Breast Carcinoma, Breast Cancer Risk Factor, Exercise, Physical Activity, Racial Differences, Women's Health. This article was prepared by Biotech Week editors from staff and other reports. Copyright 2006, Biotech Week via NewsRx.com.

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