Environment and Breast Cancer: Science Review

Evidence From Humans
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Recreational physical activity and the risk of breast cancer in postmenopausal women
McTiernan, A.,, Kooperberg, C.,, White, E.,, Wilcox, S., , Coates, R.,, Adams-Campbell, L. L., Woods, N.,, Ockene, J. JAMA. 2003. 290, 1331-1336.
Topic area
Physical Activity
Study design
Prospective Cohort
Study Participants
Number of Cases
1780 (85% invasive) (85% estrogen receptor positive)
Menopausal Status
The menopausal status of women included in this study is listed here.
Post menopausal
Number in Cohort
Cohort: 74171 (15% African American)
Cohort participation rate
Retention/participation exceeded 70% for exposed a
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: women enrolled in the WHI Observational Study; age 50-79; postmenopausal; recruited by 40 US clinical centers between 10/1993 and 12/1998; planned to live in the clinical center area for at least 3 years; free of serious health conditions Ex: women with a history of breast cancer at study entry; women with missing physical activity or covariate data
Comment about participation selection
Strengths: large prospective cohort study with many cases; analyzed a racial and ethnically diverse cohort; detailed assessment of physical activity; uniform and strict criteria for breast cancer end points; anthropometric data obtained by trained staff; study physicians and cancer coders were blind to exposure status when reviewing pathology reports; analyzed breast cancer risk by physical activity using different methods to measure physical activity; stratified results by menopausal status Limitations: fairly short follow-up of 4.7 years (mean); physical activity self-reported; too few cases to report results by race; did not collect lifetime data on physical activity; grouped exercises by intensity in questionnaire
Exposure Investigated
Exposures investigated
Physical inactivity and BMI
How exposure was measured
Questionnaire, self-administered Anthropometric measurement, researcher-administered
Exposure assessment comment
Physical activity self-reported
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Adequately controlled, confounders: age groups, BMI, HRT use, race, geographic region, income, ever breastfed, hysterectomy, family history of breast cancer, smoking status, parity, age at first birth, number of mammograms in previous 5 years, alcohol use
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Follow up: 4.7 years (mean) Effect modifiers: BMI
Strength of associations reported
Inverse association between breast cancer and women who participated in strenuous physical activity at age 35, RR=0.86(0.78-0.95) trend p=0.003
Inverse association between breast cancer and women who participated in moderate or strenuous physical activity at baseline, > 7 hr/wk vs. none, RR=0.79(0.63-0.99) trend p=.12
Inverse association between breast cancer and physical activity (> 40 hr/wk vs. none) amongst women with low a BMI (<24.3 vs. > 28.44), RR=0.63(0.43-0.93) trend=0.03