Environment and Breast Cancer: Science Review

Evidence From Humans
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Physical activity in different periods of life and the risk of breast cancer: the Norwegian-Swedish Women's Lifestyle and Health cohort study
Margolis, K. L., Mucci, L., Braaten, T., Kumle, M., Trolle Lagerros, Y., Adami, H. O., Lund, E., Weiderpass, E. Cancer Epidemiology, Biomarkers & Prevention. 2005. 14:1, 27-32.
Topic area
Physical Activity
Study design
Prospective cohort
Funding agency
NCI Other: Norwegian Cancer Society, Aakre Foundat
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number in Cohort
Cohort: 99,504 (92,638 pre) (6866 post)
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: Residents of Norway age 34-49 and residents of Sweden age 30-49 from 1990-1991; Women who participated in the Women's Lifestyle and Health Study Ex: women diagnosed with a malignant cancer; women with a lack of information on vital status; women who emigrated before follow-up; women who had missing information on physical activity variables
Comment about participation selection
Strengths: large prospective cohort with many cases; population based study; fairly lengthy follow-up of more than 9 years; high participation rate; analyzed breast cancer risk by physical activity at different stages in life Limitations: information was self-reported; physical activity was assessed differently in the two nations; did not validate the self-reported physical activity data; did not have data on the characteristics of cancer, including size, stage and receptor status; menopausal status at diagnosis was determined by age
Exposure Investigated
Exposures investigated
Sedentary lifestyle
How exposure was measured
Questionnaire, self-administered
Exposure assessment comment
Information was 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 at enrollment, education, BMI, height, smoking status, alcohol intake, age at menarche, parity, age at first birth, months of breast feeding, oc use, family history of breast cancer, menopausal status, country of or
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: 9.1 years (mean)
Strength of associations reported
Inverse association between breast cancer risk and women who had a change in their physical activity levels from inactive to active after the age of 30 to enrollment, RR=0.66(0.44-0.96)
No association between breast cancer risk and physical activity at enrollment, vigorous vs. none, RR=1.24(0.85-1.82) trend p=0.85
No association between breast cancer risk and physical activity at age 30, vigorous vs. none, RR=1.20(0.77-1.95) trend p=0.60
No association between breast cancer risk and physical activity at age 14, vigorous vs. none, RR=1.05(0.72-1.54) trend p=0.14