Environment and Breast Cancer: Science Review

Evidence From Humans
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Physical activity at age 12 and adult breast cancer risk (United States)
Marcus, P. M.,, Newman, B.,, Moorman, P.G.,, Millikan, R. C.,, Baird, D. D.,, Qaqish, B.,, Sternfeld, B. Cancer Causes and Control. 1999. 10, 293-302.
Topic area
Physical Activity
Study design
Population based case-control
Study Participants
Number of Cases
864 (527 White) (337 African-American) (375 pre) (424 post) (invasive only)
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number of Controls
Control: 790 (458 White) (332 African-American) (297 pre) (429 post)
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: participants of the Carolina Breast Cancer Study (CBCS); residents of 24 North Carolina Counties; age 20-74 years; diagnosed with primary invasive breast cancer between May 1993 and May 1996 (cases); owned a drivers license or identification card (controls 65 or younger); Medicare beneficiary (controls 65 or older);
Comment about participation selection
Strengths: large population based case-control study; analyzed breast cancer risk in Whites and African-Americans by physical activity at age 12; adjusted for confounders; Limitations: low participation rate amongst controls; does not stratify results by menopausal status; under-representation of women who are of lowered socio-economic status; participation varied across subgroups defined by age and race; physical activity measurements lacked information on frequency, intensity, and duration of activity; only measured physical activity at age 12; possible recall bias
Exposure Investigated
Exposures investigated
Lack of physical activity at age 12
Exposure assessment comment
Physical activity self reported; physical activity measurements lacked information on frequency, intensity, and duration of activity; only measured physical activity at age 12
Early life exposures considered
Physical activity at age 12
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: adult height, BMI at 18, recent BMI, change in weight, alcohol consumption, smoking status, history of radiation treatment, history of benign breast biopsy, OC use, history of miscarriage, history of induced abortion, h
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: age at menarche, body size, recent physical activity
Results Comments
Modest inverse relationship between all levels of activity relative to no reported activity (no significant association)
Controls participation rate
Less than 70% (68%