Evidence From Humans
 
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Physical exercise reduces risk of breast cancer in Japanese women
Hirose, K., Hamajima, N., Takezaki, T., Miura, S., Tajima, K. Cancer Science. 2003. 94:2, 193-9.
Topic area
Physical Activity - Body size
Study design
Other: case-referent
Funding agency
Ministry of Health, Labor and Welfare and the Mini
Study Participants
Number of Cases
2,376 (1,334 pre) (1,024 post)
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number of Controls
Referents: 18,977
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: participants of the Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC); age 30 or older at baseline; outpatient visitors of the Aichi Cancer Center in Japan between 1/1989 and 12/2000 Ex: women without information on menopausal status; women with no menstruation due to surgery; women referred to Aichi by a physician because they were thought to have cancer; women diagnosed with a previous cancer
Comment about participation selection
Strengths: Large case-referent study; assessed dietary intake with breast cancer risk; analyzed breast cancer risk according to physical exercise by BMI and menopausal status; conducted a study that compared lifestyle characteristics of the general population and outpatients; data was collected prior to diagnoses to avoid information bias; cases were confirmed by histological exam Limitations: anthropometric data and physical activity levels self-reported; possible bias due to use of hospital-based non-cancer patients as referents; lack of techniques to measure the exercise levels of individuals which poses a possible bias in physical activity reports; people who participate in regular exercise are generally more concerned with health maintenance decreasing their risk of breast cancer; did not assess the duration and the intensity of exercise; did not assess adolescent physical activity; did not assess physical activity at different periods of participants' lives
Exposure Investigated
Exposures investigated
BMI and physical inactivity
How exposure was measured
Questionnaire, self-administered
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.
Japanese Women
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, visit year, age at menarche, menopausal status, family history, parity, age at first full-term pregnancy, drinking status, intake of fruit, dietary restriction, BMI and occupation
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
No
Description of major analysis
Effect Modifiers: age, menopausal status, age at menarche, parity, family history, alcohol consumption, BMI, stomach cancer screening history. Analysis of body size used effect modifiers physical activity and menopausal status
Strength of associations reported
Inverse association between breast cancer risk and physical activity in all women, > 2 times/wk vs. none, OR=0.81(0.69-0.94) trend p=0.015
Inverse association between breast cancer risk and physical activity in women who experienced menarche at age 14 or older, > 2 times/wk vs. none, OR=0.82(0.67-0.99) trend p=0.070
Inverse association between breast cancer risk and physical activity in parous women, > 2 times/wk vs. none, OR=0.79(0.67-0.93) trend p=0.015
Inverse association between breast cancer risk and physical activity in women without a family history of breast cancer, > 2 times/wk vs. none, OR=0.81(0.69-0.94) trend p=0.021
Inverse association between breast cancer risk and physical activity in women who do not consume alcohol, > 2 times/wk vs. none, OR=0.81(0.68-0.95) trend p=0.047
No association between premenopausal breast cancer risk and physical activity , > 2 times/wk vs. none, among women with a low BMI (<22), OR=0.75(0.55-1.02) trend p=1.60
No association between postmenopausal breast cancer risk and physical activity , > 2 times/wk vs. none, among women with a low BMI (<22), OR=0.75(0.55-1.02) trend p=1.60
Results Comments
No effect modification by BMI, age, history of stomach cancer screening or by menopausal status. No effect modification seen in analysis for body size by physical activity or menopausal status.
Author address
Division of Epidemiology and Prevention, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681. khirose@aichi-cc.jp
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