Evidence From Humans
 
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Influence of physical activity in different age and life periods on the risk of breast cancer
Friedenreich, C.M.,, Courneya, K.S.,, Bryant, H.E. Epidemiology. 2001. 12, 604-612.
Topic area
Physical Activity
Study design
Population based case-control
Funding agency
Other: Canadian Breast Cancer Research Initiative
Study Participants
Number of Cases
1233 (462 pre) (771 post) (in situ and invasive only)
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number of Controls
Controls: 1237 (475 pre) (762 post)
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: women diagnosed with in situ and invasive breast cancer in Alberta, Canada between 8/95 and 8/97 (cases); resident of Alberta; younger than 80 years old; English speaking; completed interview; had a listed telephone number (controls) Ex: could not speak English; changed telephone numbers or had a disconnected telephone during the study; had incomplete interviews; diagnosed with a prior cancer; had many missing values
Comment about participation selection
Strengths: large population based case control study; cases were histologically confirmed; conducted in-person interviews; assessed diet; anthropometric data was measured by trained staff; assessed lifetime physical activity using MET (ratio of the associated metabolic rate for a specific activity compared to the resting metabolic rate); compared controls to a sample of Albertans to address the issue of selection bias due to a low participation rate from controls; analyzed breast cancer risk by physical activity stratified by menopausal status and age periods, age periods alone, and life periods (ex: birth to menarche or first pregnancy to menopause) Limitations: possible selection bias due to a low participation rate amongst controls
Exposures investigated
Physical activity
How exposure was measured
Questionnaire, in person
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
No
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.
Age, WHR, education, HRT use, history of benign breast disease, family history of breast cancer, alcohol consumption, smoking status
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 modification: time periods and life periods overall and by menopausal status (Assessment of activity in one time or life period did not adjust for activity in other time or life periods)
Strength of associations reported
Inverse association between postmenopausal breast cancer and physical activity in women who exercised 185 MET hours/wk/yr or more during the life period from menopause to reference year, OR=0.70(0.52-0.95) compared to women who exercised 103.7 MET hours/wk/yr or less
Inverse association between postmenopausal breast cancer and physical activity in women who had a total lifetime physical activity level of 134.5 MET hours/wk/yr or more, OR=0.70(0.52-0.94) compared to women with a total lifetime physical activity level of less than 86.6 MET hours/wk/yr
Inverse association between postmenopausal breast cancer and physical activity in women who exercised 56.1 MET hours/wk/yr between ages 0 and 17, OR=0.73(0.54-0.98) compared to women with less than 18.8 MET hours/wk/yr
Inverse association between postmenopausal breast cancer and physical activity in women who exercised 164.9 MET hours/wk/yr between ages 45 and 64, OR=0.72(0.54-0.97) compared to women with less than 89.0 MET hours/wk/yr
Inverse association between breast cancer and physical activity in women who were lifelong exercisers, OR=0.58(0.41-0.83) compared to nonexercisers
Controls participation rate
Less than 70% (56.5%) but rate excludes deaths, lo
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