Environment and Breast Cancer: Science Review

Evidence From Humans
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A prospective study of recreational physical activity and breast cancer risk
Rockhill, B.,, Willett, W.C.,, Hunter, D.J.,, Manson, J.E.,, Hankinson, S.E.,, Colditz, G.A. Archives of Internal Medicine. 1999. 159, 2290-2296.
Topic area
Physical Activity - Body size
Study design
Prospective cohort
Study Participants
Number of Cases
3137 (1036 pre) (2101 post) (invasive only)
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number in Cohort
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: Registered nurses who were recruited into the Nurses Health Study (NHS) established in 1976; age 30-55 years at enrollment; completed mailed questionnaire Ex: Women who reported cases for which records failed to confirm; in situ cases of breast cancer; women with missing data on physical activity
Comment about participation selection
Strengths: large prospective study; lengthy follow-up (16 years); large number of cases; evaluated the association between breast cancer and physical activity using three different measurement methods for physical activity; obtained pathology reports for 93% of the cases; questionnaires used to obtain updated information were sent every 2 years Limitations: obtained information through mailed questionnaires; anthropometric and physical activity data were self-reported; physical activity data were were taken over a 16 year period and does not reflect lifelong activity; does not include occupational physical activity in analysis
Exposure Investigated
Exposures investigated
Physical activity
How exposure was measured
Questionnaire, self-administered
Exposure assessment comment
Physical activity data were 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, age at menarche, history of benign breast disease, family history of breast cancer, height, parity, age at first birth, BMI at 18, menopausal status and postmenopausal HRT 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: 16 years
Strength of associations reported
Inverse association between breast cancer risk and women who had 7 hrs/wk on average of physical activity during follow-up vs <1 hr/wk, RR=0.81(0.69-0.95)
Inverse association between breast cancer risk and women who had 7 hrs/wk of moderate or vigorous physical activity at baseline vs <1 hr/wk, RR=0.89(0.80-0.98)
Results Comments
No significant association between breast cancer risk and vigorous physical activity