Environment and Breast Cancer: Science Review

Evidence From Humans
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Physical activity and risk of breast cancer in premenopausal women
Colditz, G. A., Feskanich, D., Chen, W. Y., Hunter, D. J., Willett, W. C. British Journal of Cancer. 2003. 89:5, 847-51.
Topic area
Physical Activity - Body size
Study Participants
Number of Cases
849 (invasive only)
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Number in Cohort
Cohort: 110,468
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 Nurses Health Study II; registered nurse; age 25 to 42 at baseline; lived within 14 US states; responded to mailed questionnaires; premenopausal Ex: previous diagnosis of cancer; diagnosed with in situ breast cancer
Comment about participation selection
Strengths: large cohort; high response rate; follow-up questionnaire sent every two years; fairly large number of cases; analyzed breast cancer risk by physical activity stratified by BMI; data on physical activity was shown to classify women reasonably well Limitations: excluding in situ cases eliminated 22% of total cases; anthropometric data self-reported; small number of cases with <3 MET h/week of physical activity
Exposure Investigated
Exposures investigated
Physical activity and BMI
How exposure was measured
Questionnaire, in person
Exposure assessment comment
Anthropometric data self-reported
Statistical Analysis
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 BMI, height, alcohol intake, age at menarche, parity, age at first birth, history of benign breast disease, family history of breast cancer, OC 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
Effect modifiers: BMI. Considered Physical activty as effect modifier in BMI analysis. Follow-up: 10 years
Strength of associations reported
No association between premenopausal breast cancer risk and physical activity, MET hr/wk > 27 vs. <3, RR=1.04(0.82-1.33) trend p=0.86
No association between premenopausal breast cancer risk and physical activity, MET hr/wk > 27 vs. <3, in women with a BMI of less than 25, RR=1.04(0.72-1.36) trend p=0.89
Premenopausal breast cancer risk and physical activity, MET hr/wk > 27 vs. <3, in women with a BMI of >30, RR=1.53(0.89-2.63) trend p=0.04
Results Comments
No overall association between breast cancer risk and physical activity in premenopausal women. Among women with a BMI >30 there was a significant positive dose-response relation (0.04). Physical activity was unrelated to breast cancer risk at lower levels of BMI.
Author address
Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA. graham.colditz@channing.harvard.edu