Environment and Breast Cancer: Science Review
About
Physical activity and the risk of breast cancer
Thune, I.,, Brenn, T.,, Lund, E.,, Gaard, M. New England Journal of Medicine. 1997. 336:18, 1269-1275.
Topic area
Physical Activity - Body size
Physical Activity - Body size
Study design
Prospective cohort
Prospective cohort
Funding agency
Other: Norwegian Cancer Society
Other: Norwegian Cancer Society
Study Participants
Number of Cases
351 (invasive only) (100 pre) (251 post)
351 (invasive only) (100 pre) (251 post)
Menopausal Status
Post menopausal
The menopausal status of women included in this study is listed here.
Pre menopausalPost menopausal
Number in Cohort
Cohort: 25,624
Cohort: 25,624
Cohort participation rate
Retention/participation exceeded 70% for exposed a
Retention/participation exceeded 70% for exposed a
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: women age 20-54 years who participated in health surveys conducted by the National Health Screening Service; resident of one of three counties in Norway (Oppland, Sogn og Fjordance or Finnmark)
Ex: women with a previous cancer diagnosis; developed cancer or died within the first year of the study
Comment about participation selection
Strengths: large prospective cohort; lengthy follow-up (13.7 years mean); included a food-frequency questionnaire in surveys; 98% of cases were verified histologically; analyzed 359,930 person years of follow-up; large number of cases; analyzed breast cancer risk according to physical activity during leisure time and work stratified by menopausal status; analyzed breast cancer risk according to physical activity stratified by BMI; population based approach; high participation rate; almost a complete reporting of cases Limitations: physical activity and anthropometric data were self-reported; did not have information on age at menarche or OC use
Strengths: large prospective cohort; lengthy follow-up (13.7 years mean); included a food-frequency questionnaire in surveys; 98% of cases were verified histologically; analyzed 359,930 person years of follow-up; large number of cases; analyzed breast cancer risk according to physical activity during leisure time and work stratified by menopausal status; analyzed breast cancer risk according to physical activity stratified by BMI; population based approach; high participation rate; almost a complete reporting of cases Limitations: physical activity and anthropometric data were self-reported; did not have information on age at menarche or OC use
Exposure Investigated
Exposures investigated
Physical Activity and BMI
Physical Activity and BMI
How exposure was measured
Questionnaire, self-administered
Questionnaire, self-administered
Exposure assessment comment
Physical activity and anthropometric data were self-reported
Physical activity and anthropometric data were self-reported
Breast cancer outcome investigated
Primary breast cancer
Primary breast cancer
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.
Adequately controlled, Confounders: age, BMI, height, parity, county of residence, age at first birth, number of children, and diet
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: menopausal status and BMI Follow-up: 13.7 yrs (median)
Effect modifiers: menopausal status and BMI Follow-up: 13.7 yrs (median)
Strength of associations reported
Decreased risk of breast cancer among women who exercise regularly during leisure time vs sedentary women, RR=0.63(0.42-0.95) trend p=0.04 (1977-1983 survey)
Decreased risk of breast cancer among women who do heavy manual labor at work vs sedentary women, RR=0.48(0.25-0.92) trend p=0.02 (1977-1983 survey)
Decreased risk of breast cancer among premenopausal women who do heavy manual labor at work vs sedentary women, RR=0.48(0.24-0.95) trend p=0.03 (1977-1983 survey)
Decreased risk of breast cancer among women with a BMI of less than 22.8 who exercise regularly during leisure time vs sedentary women , RR=0.28(0.11-0.70) trend p=0.02 (1977-1983 survey)
Decreased risk of breast cancer among women with a BMI of less than 22.8 who are consistently active during leisure time vs. sedentary women, OR=0.23(0.09-0.60) trend p=0.002 (1974-1978 and 1977-1983 surveys)
Decreased risk of breast cancer among women who exercise regularly during leisure time vs sedentary women, RR=0.63(0.42-0.95) trend p=0.04 (1977-1983 survey)
Decreased risk of breast cancer among women who do heavy manual labor at work vs sedentary women, RR=0.48(0.25-0.92) trend p=0.02 (1977-1983 survey)
Decreased risk of breast cancer among premenopausal women who do heavy manual labor at work vs sedentary women, RR=0.48(0.24-0.95) trend p=0.03 (1977-1983 survey)
Decreased risk of breast cancer among women with a BMI of less than 22.8 who exercise regularly during leisure time vs sedentary women , RR=0.28(0.11-0.70) trend p=0.02 (1977-1983 survey)
Decreased risk of breast cancer among women with a BMI of less than 22.8 who are consistently active during leisure time vs. sedentary women, OR=0.23(0.09-0.60) trend p=0.002 (1974-1978 and 1977-1983 surveys)