Environment and Breast Cancer: Science Review

Evidence From Humans
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Birthweight as a risk factor for breast cancer
Michels, K. B., Trichopoulos, D., Robins, J. M., Rosner, B. A., Manson, J. E., Hunter, D. J., Colditz, G. A., Hankinson, S. E., Speizer, F. E., Willett, W. C. Lancet. 1996. 348:9041, 1542-6.
Topic area
Early life exposures
Study design
Nested case-control
Funding agency
NCI and the Massachusetts Department of Public Hea
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Number in Cohort
Controls: 1569, cohort: 238,380
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Nurses Health Study I and II (NHS) In: Registered nurses born between 1921 and 1945 participating to the NHS I and born between 1946 and 1965 and participating to the NHS II. Case: nurses from both cohorts with confirmed invasive or in situ breast cancer who were alive and had not indicated in previous questionnaires that their mothers had died. Controls: matched for year of birth and cohort, and who did not have breast cancer Ex: Participants with mothers who had died, had Alzheimer's disease, memory loss, or senile dementia, or otherwise incapable of responding to a questionnaire, who was not the biological mother or did not speak english or refused to paticipate to the study. Women with in situ breast cancer, diagnosis of breast cancer was not confirmed and mothers of cases who did not report their date of birth
Exposure Investigated
Exposures investigated
Birthweight, premature birth
How exposure was measured
Other: Reported by mothers of participants
Exposure assessment comment
Accuracy of reported information for premature birth before1965
Statistical Analysis
Breast cancer outcome investigated
Primary incident breast cancer
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.
Race, alcohol consumption
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
Logistic regression model. Adult or other perinatal variables were considered. Selection for inclusion in the models was based on biological plausibility and evidence of confounding. Final model adjusted for age, cohort, parity, age at first birth, age at
Strength of associations reported
Birthweight: 0.55 (0.33-0.93); premature birth: 1.04 (0.46-2.38)
Results Comments
Increasing birthweight was associated with increasing risk of breast cancer. However the apparent birthweight effect was appreciable only at the extreme tails of the distribution. Prematurity itself was not found to be associated with risk of breast cancer.
Author address
Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA.