Environment and Breast Cancer: Science Review

Evidence From Humans
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Recreational physical activity and risk of postmenopausal breast cancer in a large cohort of US women
Patel, A. V.,, Calle, E. E.,, Bernstein, I.,, Wu, A. H.,, Thun, M. J. Cancer Causes and Control. 2003. 14, 519-529.
Topic area
Physical Activity
Study design
Prospective cohort
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Post menopausal
Number in Cohort
Cohort: 72,608
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: participants of the American Cancer Society Cancer Prevention Study II (CPS-II) Nutrition Cohort established in 1992; age 50-74 (greater majority) Ex: women lost to follow-up; cases with a missing year of diagnosis; women who reported a prevalent breast cancer at baseline; women who were not post-menopausal in 1992; women with missing exercise data
Comment about participation selection
Strengths: Large prospective cohort with many cases; high participation rate; used MET (ratio of metabolic rate during a specific activity to resting metabolic rate) to assess physical activity; assessed the association between postmenopausal breast cancer stage and physical activity; assessed effect modification with several risk factors; tested for potential confounders; obtained caloric intake information Limitations: self-administered questionnaire with self-reported physical activity; fairly short follow-up of five years; lack of information on physical activity during adolescent years; lacked updated information during follow-up; did not assess individual information on intensity of physical activity; participants tended to be more health conscience than average
Exposure Investigated
Exposures investigated
Sedentary lifestyle
How exposure was measured
Questionnaire, self-administered
Exposure assessment comment
Self-administered questionnaire with self-reported physical activity
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, race, BMI, weight change from 18 years to 1992, family history of breast cancer, personal history of benign breast cycsts, duration of oc use, HRT use, parity, age at menarche, age at menopause, smoking status, alc
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: 5 years Analyzed stage at diagnosis Effect modifiers: age, HRT use, alcohol intake, caloric intake, weight change from 18 years to 1992, BMI
Strength of associations reported
No significant association between postmenopausal breast cancer and physical activity at baseline, MET hr/week >42.0 vs. 7.0-17.5, RR=0.71(0.49-1.02) trend p=0.03
No significant association between postmenopausal breast cancer and physical activity at age 40, MET hr/week >42.0 vs. 7.0-17.5, RR=0.79(0.61-1.03) trend p=0.36
Inverse association between localized postmenopausal breast cancer and physical activity, MET hr/week >42.0 vs. 7.0-17.5, RR=0.55(0.38-0.80) trend p=0.02
Effect modification between women who had never used HRT and physical activity, MET hr/week >42.0 vs. 7.0-17.5, RR=0.64(0.43-0.97) trend p=0.09